library 


ELECTRIC   IGNITION 


FOR 


COMBUSTION   MOTORS 


BY 

FORREST    R.   JONES,    M.E. 

Member  of  the   A  merican   Society   of  Mechanical  Engineers,  and  of  the   Society  for 

the  Promotion  of  Engineering  Education.      Formerly  Professor  of  Mechanic 

Arts  in  the  University  of  Tennessee,  and  of  Machine  Design  successively 

in  the  University  of  Wisconsin,  the   Worcester  Polytechnic  • 

Institute  and  Cornell   University 


FIRST  EDITION 

FIRST    THOUSAND 


• 


NEW  YORK 

JOHN   WILEY  &    SONS 

LONDON:   CHAPMAN  &   HALL,   LIMITED 

1912 


COPYRIGHT,  1912, 

BY 
FORREST  R.  JONES 


Stanhope  ipms 

F.   H.  GILSON     COMPANY 
BOSTON.     U.S. A 


/  ^'773 


Engineering 
Library 


PREFACE. 


THE  plan  of  this  work  is  based  upon  the  supposition  that 
some  of  its  readers  may  possibly  be  unfamiliar  with  electricity 
and  electrical  devices.  To  meet  this  condition,  the  fundamen- 
tal principles  involved  in  each  case  are  given  before  commercial 
forms  are  described. 

The  range  of  the  subject  matter  is  from  the  small  ignition 
apparatus  used  on  motor  cycles  to  that  used  on  the  largest  gas 
engines. 

More  than  half  of  the  illustrations  have  been  prepared  espe- 
cially for  the  book,  largely  from  sketches,  drawings,  photographs, 
and  information  kindly  furnished  by  those  making  or  dealing  in 
ignition  appliances. 

Electric  connections,  both  internal  and  external,  are  shown, 
by  wiring  diagrams  and  other  means,  for  complete  ignition  sys- 
tems and  the  parts  of  which  they  are  composed. 

Considerable  attention  is  given  to  the  operation,  care,  adjust- 
ment, and  testing  of  ignition  systems  and  their  various  parts. 
Lack  of  knowledge  in  this  respect  is  the  chief  cause  of  ignition 
troubles  in  connection  with  the  excellent  equipments  now  ob- 
tainable. 

FORREST  R.  JONES. 

KNOXVILLE,  TENNESSEE, 
January,  1912. 


257830 


CONTENTS. 


CHAPTER  I. 
INTRODUCTORY. 

ART.  PAGE 

1.  Electric  ignition  in  general i 

2.  High-tension  and  low-tension  electricity i 

3.  Sources  of  electricity 3 

4.  Permanent  magnets.     Forms  and  action 3 

5.  Poles  of  a  magnet 5 

6.  Magnetic  field 6 

7.  Magnet  keeper  and  its  effect 6 

8.  Magnetic  and  non-magnetic  materials 7 

9.  Compound  or  composite  magnets 8 

10.  Principle  of  electric  generators & 

11.  Armature  of  electric  generator 9 

CHAPTER  II. 

LOW-TENSION  ALTERNATING-CURRENT  MAGNETOS  WITH 
SINGLE-WOUND   SHUTTLE  ARMATURES. 

12.  Field  magnets  of  a  magneto 10 

13.  Abutted  magnets n 

14.  Armature  of  magneto n 

15.  Electric  arc  from  a  shuttle-wound  armature 14 

16.  Effect  of  speed  of  armature  on  position  for  maximum  arc 16 

17.  Positions  of  armature  for  strong  electric  arc 16 

18.  Laminated  armature  core 18 

19.  Magnetic  flux  in  a  rotating  I-shaped  armature  core 19 

20.  Electromotive  force  and  current  induced  in  an  armature 24 

21.  Armature  lag 24 

22.  Alternating  current  generated 25 

23.  Graphical  representation  of  current  in  a  shuttle-wound  armature 28 

24.  Cycle  of  current 29 

25.  Form  of  current  curve  as  affected  by  shape  of  pole-pieces 29 

26.  Position  of  armature  for  maximum  arc 30 

27.  Low-tension  alternating-current  magneto  with  shuttle- wound  armature  31 

28.  Stationary  armature  and  rotary  magnetic  sleeve 35 

29.  Action  of  the  magnetic  sleeve 37 

30.  Note  regarding  low- tension  magnetos  for  high-tension  ignition 37 

CHAPTER  III. 
DIRECT-CURRENT  MAGNETOS. 

31.  General 38 

32.  Elementary  form  of  drum  armature , 39 

33.  Generation  of  current 39 

34.  Commutation  of  current  in  a  direct-current  generator 41 

35.  Continuous-current  electric  generator 43 

36.  Laminated  drum  armature  core 43 

v 


VI  CONTENTS 

ART.  PAGE 

37.  Complete  drum  armature 44 

38.  Commutator  for  direct-current  generator 44 

39.  Armature  connections 45 

40.  Complete  direct-current  magneto 48 

CHAPTER  IV. 
TESTING  FOR  DIRECTION   OF  CURRENT. 

41.  Water  test.     Bubbles  at  submerged  wire-end 50 

42.  Color  test 51 

43.  Magnetic  compass  test 52 

44.  Extemporized  compass  needle 53 

45.  Test  with  measuring  instruments v 53 

CHAPTER  V. 
ELECTRIC   MEASURING  INSTRUMENTS. 

46.  General 54 

47.  Ammeters 54 

48.  Voltmeters 56 

49.  Volt-ammeters 57 

50.  Dead-beat  indicating  needle 59 

CHAPTER  VI. 
ELECTROMAGNETS. 

51.  Plain  bar  electromagnet 60 

52.  Plunger-core  electromagnet 61 

53.  U-shaped  electromagnet 62 

54.  Ring-shaped  electromagnet  with  consequent  poles 64 

55.  Bipolar  ring-shaped  electromagnet 64 

56.  Four-pole  ring-shaped  electromagnet 64 

CHAPTER  VII. 
DIRECT-CURRENT   GENERATORS  WITH  ELECTROMAGNETS. 

57.  General 65 

58.  Bipolar  direct-current  generator  with  U-shaped  shunt-wound  electro- 

magnets    65 

59.  Bipolar  direct-current  generator  with  ring-shaped  shunt-wound  electro- 

magnets    67 

60.  Four-pole  direct-current  generator  with  shunt- wound  electromagnets.  .  .  71 

61.  Series-and-shunt  field  winding - 74 

62.  Field  rheostat  for  regulating  voltage 75 

63.  Reversing  the  rotation  of  the  armature 76 

CHAPTER  VIII. 
PRIMARY  BATTERIES. 

64.  Carbon-zinc  battery 78 

65.  Elementary  Leclanche  carbon-zinc  wet  cell 78 

66.  Polarization  of  primary  electric  cell 80 

67.  Dry  cell  with  carbon  and  zinc  electrodes 80 


CONTENTS  Vll 

ART.  *AGE 

68.  Deterioration  of  dry  batteries  while  idle 82 

69.  New  type  of  carbon-zinc  dry  cell 82 

70.  Exhaustion  of  dry  batteries  in  service 83 

71.  Recuperation  of  dry  cells 83 

72.  Lalande  and  Chaperon  wet  cell 84 

73.  BSCO  wet  cell 84 

74.  Edison  primary  battery 86 

CHAPTER  IX. 
BATTERY   CONNECTIONS. 

75.  General 88 

76.  Series-connected  battery  of  four  cells . . . 88 

77.  Reversed  cell  in  a  series  battery 89 

78.  Parallel-connected  battery  of  four  cells 90 

79.  Reversed  cell  in  a  parallel-connected  battery 91 

80.  Parallel-series  batteries 92 

81.  Wrong  arrangement  of'  a  battery 93 

82.  Connection  to  external  circuit 94 

83.  Screw-top  battery  cells . 95 

CHAPTER  X. 

STORAGE  BATTERIES,  ALSO  CALLED  ACCUMULATORS 
AND  SECONDARY  BATTERIES. 

84.  Storage  battery  defined 97 

85.  Electrodes,  or  plates,  of  a  lead  storage  cell 98 

86.  Complete  storage  cell 99 

87.  Voltage  of  a  storage  cell  having  lead  plates 101 

88.  Maximum  rate  of  discharge  of  storage  cell 102 

89.  General  description  of  storage  battery .^ 102 

90.  Exide  storage  battery 104 

91.  Charging  the  storage  battery 107 

92.  Chemical  action  in  a  lead  storage  battery 108 

93.  Capacity  of  a  storage  cell 109 

CHAPTER  XI. 

FLOATING  THE  STORAGE  BATTERY  ON  THE  LINE  OF  A 
DIRECT-CURRENT   GENERATOR. 

94.  Method  of  floating  the  battery  on  the  line no 

95.  Automatic  cut-out 113 

96.  Two- voltage  system  with  two  storage  batteries  floated  on  the  line 117 

97.  Two-voltage  system  with  lamps  and  ignition  apparatus 118 

98.  Switchboard  for  two- voltage  system  with  battery  floated  on  the  line  .  .  119 

CHAPTER  XII. 

MECHANICALLY    OPERATED    MAKE-AND-BREAK    IGNITERS 
AND  KICK-COILS  FOR  LOW-TENSION  IGNITION. 

99.  Mechanically  operated  igniter : 123 

100.  Duration  of  contact  between  the  electrodes 126 

101.  Bosch  mechanically  operated  igniter 126 

102.  Truscott  Boat  Manufacturing  Company's  igniter 128 


viii  CONTENTS 

ART.  PAGE 

103.  Fay  &  Bowen  low-tension  igniter 131 

104.  Westinghouse  make-and-break  igniters 132 

105.  Snow  Steam  Pump  Works  mechanically  operated  igniter 133 

106.  Mechanical  make-and-break  operating  mechanism  of  the  Snow  Steam 

Pump  Works  igniter 133 

107.  Four-unit  low-tension  mechanism 137 

108.  Allis-Chalmers  gas  engine  with  mechanical  make-and-break  igniters..  .  138 

109.  Kick-coils 138 

1 10.  Screw-top  kick-coil . 142 

in.  Tell-tale  kick-coil 142 


CHAPTER  XIII. 

MECHANICAL  MAKE-AND-BREAK  LOW-TENSION  IGNITION 
SYSTEMS. 

112.  Battery,  reactance  coil,  and  make-and-break  igniter 144 

113.  Duration  of  contact 145 

114.  Magnet  and  make-and-break  igniter 146 

115.  Direct-current  generator,  kick-coil,  and  mechanical  make-and-break  ig- 

niter        148 

116.  System  for  four  combustion  chambers.     Mechanical  make-and-break 

igniter,  storage  battery,  primary  battery,  and  direct-current  generator     149 

117.  Alternating-current  magneto,  primary  battery,  and  four  make-and- 

break  igniters 150 

118.  Storage  battery  floated  on  the  line  of  a  shunt-wound  generator,  and 

mechanical  make-and-break  igniters 151 

119.  no- volt  generator  and  6- volt  primary  battery  mechanical  make-and- 

break  system 152 

1 20.  Multiple  system  with  switchboards,  primary  batteries,  and  no- volt 

direct-current  generator 155 

121.  Storage  battery  and   no- volt  generator  mechanical  make-and-break 

system 159 

122.  Storage  battery,  primary  battery,  and  no- volt  generator  make-and- 

break  system 160 

123.  Multiple  system  with  storage  batteries,   no-volt  generator,  primary 

battery,  and  switchboards 161 

124.  System   using   current   from   no-volt  direct-current   service   without 

ground  connection 162 

125.  Multiple  system  using  iio-volt  to  125-volt  direct  current  from  general 

service  circuit 165 

126.  Triple  low- tension  ignition  system  for  large  engine  with  four  double- 

acting  cylinders 165 

CHAPTER  XIV. 

ELECTROMAGNETIC  IGNITERS  AND  IGNITION  SYSTEMS  FOR 
LOW-TENSION   CURRENT. 

127.  Principle  of  operation 169 

128.  Elementary  ignition  system  with  a  timer  and  an  igniter  having  an  elec- 

tromagnet with  a  plunger  core 169 

129.  Dual  ignition  system  with  plunger-core  electromagnets  in  the  igniter.  .      171 

130.  Wisconsin  Engine  Company's  electromagnetic  igniter  with  plunger  cores. 

Details 175 

131.  Details  of  one-ring  timer  for  large  engine  with  four  combustion  cham- 

bers        1 78 


CONTENTS  ix 

ART.  PAGE 

132.  Allis-Chalmers  four-ring  timer  for  large  engine 181 

133.  Details  of  Allis-Chalmers   electromagnetic   igniter  for   a  large  engine  184 

134.  Wiring  diagram  for  a  four-ring  timer  and  igniters  actuated  by  a  rotary 

magnet  armature 191 

135.  Bosch  igniter  with  vibratory  magnet  armature 191 

136.  Magneto  and  wiring  diagram  for  magnetic-plug  ignition  system 194 


CHAPTER  XV. 

TRANSFORMER  SPARK-COILS  AND  SYNCHRONIZER,  OR  MASTER, 
TREMBLER-COILS. 

137.  General 200 

138.  Elementary  transformer  spark-coils 200 

139.  Operation  of  elementary  transformer  spark-coil  without  trembler 202 

140.  Trembler  transformer  spark-coil 204 

141.  Safety  spark-gap 213 

142.  Lag  of  spark-coils 214 

143.  Tremblers,  or  vibrators:  Bow-spring,  hammer-break,  and  plain  types. .  .  214 

144.  Complete  trembler  transformer  spark-coils 220 

145.  Synchronized  spark-coils  with  master-trembler 222 

146.  Trembler  spark-coil  for  use  with  high-tension  distributor 223 

147.  Plain  transformer  spark-coils  without  a  trembler 224 

148.  Connections  to  trembler  spark-coils 225 


CHAPTER  XVI. 
TIMERS  AND  SPARK-PLUGS  FOR  HIGH-TENSION  IGNITION. 

149.  Elementary  form  of  timer 227 

150.  Roller-contact  timer 227 

151.  Sliding-contact  timer 230 

152.  Timer  with  normal-pressure  contacts 230 

153.  Spark-plugs.     General  description 231 

154.  Single-gap  jump-spark  plugs 231 

155.  Spark-plugs  with  two  or  more  spark-gaps 234 

156.  Separable  spark-plugs 236 

157.  Width  of  spark-gap 238 

CHAPTER  XVII. 

IGNITION  SYSTEMS  WITH  MAGNETIC  TREMBLER  INTERRUPTERS 
AND   INDIVIDUAL  TRANSFORMERS. 

158.  Introductory 240 

159.  System  with  one  spark-plug  and  trembler  spark-coil 240 

160.  Auxiliary  condenser  in  an  ignition  system 242 

161.  Grounded  spark-coil  condenser ;  .  243 

162.  Individual  trembler-coil  systems 244 

163.  Synchronized  system  with  master  trembler-coil 245 

164.  Synchronized  system  with  master  trembler-coil  and  auxiliary  condensers  247 

165.  Ammeter  and  voltmeter  permanently  in  the  circuit  of  a  high-tension 

ignition  system 249 

166.  Speed  of  the  timer 251 


CONTENTS 


CHAPTER  XVIII. 
HIGH-TENSION  DISTRIBUTOR  SYSTEMS  WITH  BATTERY  CURRENT. 

ART.  PAGE 

167.  General 252 

168.  High-tension  distributor  system  with  trembler  spark-coil 252 

169.  Mechanically  operated  contact-maker  and  high-tension  distributor  sys- 

tem with  battery  current 254 

1 70.  Unisparker 255 

171.  Combined  contact-maker,  spark-coil,  and  distributor 258 

172.  Comparison  of  unisparker  and  ordinary  timer 260 

CHAPTER  XIX. 
SPARK-PLUGS  IN   SERIES  AND   IN   SERIES-SHUNT. 

173.  Method  of  operating 261 

174.  Series-shunt  connection  of  spark-plugs 262 

175.  Constructive  form  of  series-shunt  spark-plug  ignition  system 265 

CHAPTER  XX. 

INTERRUPTER  MAGNETOS  AND  JUMP-SPARK  IGNITION  SYSTEMS 
WITH  MAGNETO   CURRENT  ONLY. 

176.  Introductory 268 

177.  Interrupted  primary-current  magneto  ignition  system 268 

178.  Interrupted  shunt-current  magneto  ignition  system 271 

179.  Shunted-current  magneto  ignition  system 272 

180.  High-tension  magneto  with  single-wound  armature 272 

181.  Double-wound  high-tension  magneto 273 

182.  Bosch  high-tension  magneto  with  double- wound  rotary  armature 275 

183.  U.  &  H.  magneto  with  rotary  double-wound  shuttle  armature 291 

184.  Remy  magneto  with  stationary  armature  and  rotary  inductor 295 

185.  Effect  of  advance  and  retard  on  the  strength  of  the  ignition  spark 301 

186.  Charged-and-discharged  condenser  ignition  system 302 

187.  Shaft  couplings  for  advancing  and  retarding  the  ignition 303 

187.1  Eisemann     high-tension     magneto    with     automatic    spark-advance 

mechanism 305 

188.  Interrupted  short-circuit  magneto 307 

189.  Movable  extensions  of  magnet  poles  for  constant  strength  of  spark.  . .  .  309 

190.  Pittsfield  magneto  with  stationary  armature  and  rocking  pole-extensions  311 

191.  Mea  magneto  with  rocking  magnets 316 

CHAPTER  XXI. 
HIGH-TENSION  DUAL  AND    COMBINED   IGNITION   SYSTEMS. 

192.  Introductory 326 

193.  Remy  ignition  system  with  separate  transformer 327 

194.  Splitdorf  ignition  system  with  separate  transformer 330 

195.  Eisemann  ignition  system  with  separate  transformer 334 

196.  Eisemann-Carpentier  ignition  system 337 

197.  Bosch  dual  ignition  system 340 

197. i  Duplex  high-tension  ignition  system  having  a  battery  in  series  with 

the  primary  of  the  magneto 345 

198.  Magneto  with  two  high-tension  windings  for  dual  ignition 352 


CONTENTS  XI 

CHAPTER  XXII. 
HIGH-FREQUENCY  ALTERNATING-CURRENT  MAGNETOS. 

ART.  PAGE 

199.  Introductory 353 

200.  W.  &  S.  magneto 353 

201.  K-W  high-frequency  magneto  . 356 

202.  Ford  high-frequency  magneto 358 

CHAPTER  XXIII. 
VARYING  THE  TIME   OF  IGNITION.     MULTIPLE  IGNITION. 

203.  Advancing  the  timer  on  account  of  lag  in  the  ignition  apparatus 361 

204.  Varying  the  time  of  ignition  relative  to  the  rate  of  combustion  of  the 

charge  in  the  motor 362 

205.  Varying  the  time  of  ignition  with  variable  speed 364 

206.  Reduction  of  the  variation  of  ignition  by  the  use  of  two  simultaneous 

ignition  sparks 365 

207.  Advancing  and  retarding  the  spark  in  a  variable-speed  motor 366 

CHAPTER  XXIV. 
CARE  AND   ADJUSTMENT   OF  IGNITION   SYSTEMS. 

208.  Introductory 368 

209.  Cleaning  the  spark-plug 369 

210.  Adjusting  the  width  of  spark-gap  in  jump-spark  igniters 369 

211.  Repairing  the  spark-points  of  contact  igniters 370 

212.  Adjusting  the  trembler 370 

213.  Lubricating  and  cleaning  the  timer 371 

214.  Care  of  the  magneto  or  dynamo 372 

215.  Filing  or  dressing  the  contact-points 374 

216.  Care  of  batteries  in  general 374 

217.  Keeping  electric  connections  tight 375 

218.  Testing  a  primary  battery 376 

CHAPTER  XXV. 
TESTING   OF  STORAGE  BATTERIES. 

219.  Voltage-and-current  test  of  a  storage  battery 378 

220.  Ammeter  in  series  with  resistance 379 

221.  Lamp  for  testing 381 

222.,  Testing  cells  individually 381 

223.  Voltmeter  test  of  a  storage  battery 381 

224.  Voltage-drop  test 381 

225.  Lowest  safe  voltages  of  storage  batteries  while  discharging 382 

226.  Curve  of  voltage  drop  while  a  storage  battery  is  discharging 383 

227.  Testing  the  density  of  the  electrolyte 384 

CHAPTER  XXVI. 
CHARGING  AND   CARE   OF  STORAGE  BATTERIES. 

228.  Precautions 387 

229.  Connections  for  charging  a  storage  battery 387 

230.  Connections  for  charging  two  batteries  at  the  same  time 389 

231.  Rate  of  charging  a  storage  battery 390 


xii  CONTENTS 

ART.  PAGE 

232.  Charging  and  care  of  lead-plate  storage  batteries 390 

233.  Removing  the  sediment  from  lead-plate  cells 393 

234.  Taking  a  lead-plate  cell  out  of  commission 394 

235.  Charging  and  care  of  nickel-iron  storage  batteries 394 

236.  Taking  a  nickel-iron  battery  out  of  commission 396 

CHAPTER  XXVII. 
TIMING  THE  IGNITION. 

237.  General  features 397 

238.  Timing,  or  setting,  the  timer 398 

239.  Timing  a  rotary  magneto  of  the  interrupter  type 400 

240.  Relative  positions  of  the  crank-shaft  and  piston  of  a  motor 402 

CHAPTER  XXVIII. 
IGNITION   SYSTEM   FAULTS  AND   REMEDIES. 

241.  Defects  and  conditions  in  the  ignition  system  which  cause  faulty  ignition  405 

242.  In  the  igniter 405 

243.  In  the  spark-coil  407 

244.  In  the  reactance  coil,  or  kick-coil 408 

245.  In  the  timer 408 

246.  In  the  magneto 409 

247.  In  the  dynamo 413 

248.  In  the  battery 413 

249.  In  the  connections 415 

CHAPTER  XXIX. 
OPERATING  TROUBLES  POSSIBLY  DUE  TO  THE  IGNITION  SYSTEM. 

250.  Introductory 416 

251.  Motor  will  not  start 416 

252.  Preignition 416 

253.  Back-firing  into  the  intake  of  the  motor 417 

254.  Overheating  of  the  motor 418 

255.  Misfiring  and  exhaust  explosions  without  other  serious  troubles 418 

256.  Knocking  or  pounding 419 

257.  Sudden  stoppage  of  motor 419 

258.  Motor  does  not  develop  full  power 419 

259.  Spark  control  must  be  advanced  more  than  usual,  and  motor  behaves 

erratically 420 


ELECTRIC   IGNITION. 


CHAPTER  I. 
INTRODUCTORY. 

1.  Electric  ignition,  as  applied  to  motors,  or  engines,  which 
burn  a  combustible  mixture  of  gas  inside  of  the  cylinder  of  the 
motor,  is  accomplished,  in  modern  practice,  either  by  producing 
an  electric  spark,  or  by  drawing  an  electric  arc,  inside  of  the 
cylinder  in  the  inclosed  space  which  is  filled  with  the  combustible 
mixture.     The  spark,  or  arc,  as  the  case  may  be,  ignites  the  com- 
bustible mixture  and  causes  it  to  burn. 

High-tension  and  Low-tension  Electricity. 

2.  There  are  two  classes  of  electric  ignition  as  applied  to 
combustion  motors.     One  class  is  known  as  high-tension,  or 
jump-spark,  ignition;  the  other  class  as  low-tension,  make-and- 
break,  contact,  or  touch-spark  ignition. 

The  terms  "  high-tension  "  and  "  low-tension  "  are  used  in 
accordance  with  the  intensity  of  the  tension,  also  called  pressure, 
of  the  electricity  that  is  used  to  produce  the  spark,  or  arc,  for 
igniting  the  combustible  charge.  An  idea  of  the  distinction 
between  high-tension  and  low-tension  electricity  as  used  for 
ignition  can  be  obtained  from  its  action  on  the  animal,  or  human, 
body. 

The  high-tension  electricity  used  for  ignition  is  capable  of 
giving  a  very  severe  shock  to  one  who  touches  the  metal  of  a  wire 
or  apparatus  which  is  charged  with  the  high-tension  electricity. 
The  shock  is  not  dangerous,  however,  unless  continued  for  a 
considerable  time. 

The  low-tension  electricity  for  ignition  in  motors  used  on 
automobiles,  traction  engines,  and  other  similar  appliances  is 


2  ELECTRIC  IGNITION 

hardly  capable  of  making  its  presence  known  by  giving  a  shock 
to  one  touching  the  bare  portions  of  electric  conductors  charged 
with  it,  when  ordinary  conditions  exist.  The  same  is  in  general 
true  qf  the  electricity  used  for  low-tension  ignition  in  stationary 
engines  when  the  electricity  is  supplied  by  apparatus  especially 
adapted  to  ignition  usage.  The  pressure  of  the  electricity  sup- 
plied by  such  means  for  low-tension  ignition  varies  considerably 
in  different  systems.  Some  systems  operate  on  about  4  volts, 
while  others  operate  at  about  50  volts.  The  latter  pressure  is 
about  the  same  as  that  used  in  some  commercial  lighting  systems, 
and  gives  only  a  slight  shock  under  ordinary  conditions.  Some 
stationary  engines  take  electricity  from  commercial  service  mains 
at  a  pressure  of  about  no  or  even  220  volts.  In  such  cases  the 
electric  current  is  generally  passed  through  incandescent  lamps 
which  utilize  a  portion  of  the  electric  pressure  and  prevent,  by 
their  electric  resistance,  too  much  current  from  passing  through 
the  ignition  apparatus. 

The  reason  that  the  high-tension  electricity  used  for  ignition 
is  not  dangerous,  although  its  pressure  is  several  thousand  volts, 
is  that  the  apparatus  used  does  not  have  capacity  to  furnish 
enough  electricity  to  do  serious  harm.  The  pressure  is  enor- 
mously high,  as  compared  with  that  in  service  wires  for  incan- 
descent lighting,  but  the  quantity  of  electricity  is  minutely  small. 

The  condition  of  the  skin  where  it  comes  into  contact  with 
an  electrically  charged  metal  wire  or  piece  of  apparatus  has  much 
to  do  with  the  extent  of  the  shock  that  is  received,  especially 
when  the  pressure  is  as  low  as  that  generally  used  for  incan- 
descent lighting  and  for  low-tension  ignition.  When  the  skin 
is  dry  or  oily,  the  shock  is  very  much  less  than  when  it  is  moist 
or  wet.  If  the  skin  is  cut  or  deeply  scratched  so  that  the  raw 
flesh  comes  into  contact  with  the  charged  metal,  then  the  shock 
is  still  more  severe  than  when  the  skin  is  intact  but  wet.  The 
animal  skin,  or  cuticle,  offers  more  resistance  to  the  passage  of 
electricity  than  the  other  parts  of  the  body,  at  least  the  soft 
parts.  When  the  skin  is  removed,  more  electricity  will  pass 
through  the  body  than  when  the  skin  is  intact,  even  though 
moist  or  wet  with  water.  In  other  words,  a  wet  skin  allows  more 


INTRODUCTORY  3 

electric  current  to  pass  through  it,  on  account  of  its  lesser  resist- 
ance, than  will  pass  through  when  the  skin  is  dry  or  oily  and 
consequently  offers  greater  resistance  to  the  passage  of  electricity. 

Sources  of  Electricity. 

3.  The  electricity  used  for  ignition  is  obtained  either  from  a 
power-driven  machine,  called  an  electric  generator,  or  from  an 
electric  battery  in  which  the  electricity  is  produced  by  chemical 
action. 

When  an  electric  generator  has  permanent  magnets,  it  is  gen- 
erally called  a  magneto.  An  electric  generator  which  does  not 
have  permanent  magnets  is  ordinarily  called  either  a  dynamo 
or  an  electromagnetic  generator.  Magnetos  and  electromag- 
netic generators  are  both  further  classified  according  to  the 
nature  of  the  electricity  they  produce.  This  will  be  taken  up 
in  connection  with  the  discussion  of  electric  generators. 

Electric  batteries  are  of  two  distinctive  kinds,  known  as 
primary  and  secondary.  A  secondary  battery  is  also  called  an 
electric  accumulator  and  a  storage  battery. 

A  primary  battery  is  one  which  is  ready  to  give  out  electric 
current  as  soon  as  it  is  constructed. 

A  storage  battery  cannot  give  out  electric  current  as  soon  as 
it  is  mechanically  constructed,  but  must  have  electricity  charged 
into  it  before  it  is  ready  to  deliver  electric  current.  It  must 
also  be  frequently  recharged  with  electricity  during  its  life. 

Each  unit  of  which  an  electric  battery  is  made  up  is  called 
an  electric  cell.  A  primary  electric  cell  is  also  called  a  galvanic 
cell  and  a  voltaic  cell,  after  the  names  of  its  inventors.  It  is 
quite  common  practice  to  call  an  electric  cell  a  battery,  or  a 
battery  cell. 

Permanent  Magnets. 

4.  Forms  and  Action.  —  Doubtless  the  most  familiar  forms  of 
permanent  magnets  are  the  horseshoe  magnet  and  the  magnetic 
needle.     The  latter  is  part  of  the  magnetic  compass  for  deter- 
mining the  directions  of  north  and  south.      Small   horseshoe 
magnets  are  sold  in  toy  stores  and  hardware  stores.     The  mag- 


ELECTRIC  IGNITION 


netic  compass  is  regularly  used  on  board  ocean-going  vessels,  in 
surveying  instruments,  and  in  pocket  compasses. 

A  common  form  of  horseshoe  magnet  is  shown  in  Fig.  i .  It 
is  made  of  a  piece  of  bar  steel  bent  to  bring  the  ends  of  the  bar 
near  together.  After  bending,  the  steel  is  first  hardened  and 
then  magnetized.  The  magnet  will  attract  pieces  of  iron  and 


FIGS,  i,  2,  and  3. 
Horseshoe  Magnets.     Permanent. 

steel  placed  near  the  ends  of  the  bent  bar,  and,  if  the  pieces  are 
free  to  move,  they  will  be  drawn  up  against  the  magnet  and 
held  there.  It  is  immaterial  what  forms  the  pieces  of  iron  and 
steel  to  be  attracted  have.  They  may  be  in  the  form  of  wire 
nails,  tacks,  balls  such  as  used  in  ball  bearings,  rings,  or  any 
other  form.  There  is  little  or  no  magnetic  attraction  in  the 
region  of  the  crown,  or  curve,  of  the  bent  bar. 

Nails  or  tacks  of  comparatively  mild  steel  or  soft  iron  do  not 
remain  magnetic  to  any  great  extent  after  they  are  removed 
from  the  magnet.  But  hardened  or  tempered  pieces  of  steel, 
especially  those  of  an  elongated  form,  such  as  a  knife  blade, 
sewing  needle,  and  writing  pen,  retain  considerable  magnetism 
for  some  time  after  removal  from  the  magnet,  and  will  pick  up 


INTRODUCTORY  5 

tacks  and  other  small  pieces  of  steel.  Still  harder  pieces  of  steel, 
such  as  a  file,  will  retain  magnetism  for  a  longer  time  than  the 
articles  just  mentioned. 

6.  Poles  of  a  Magnet.  —  The  usefulness  of  the  magnetic  com- 
pass depends  on  the  fact  that  one  end  of  the  magnetic  needle, 
and  that  always  the  same  end,  points  approximately  in  the  direc- 
tion of  the  north  pole  of  the  earth  when  the  needle  is  allowed  to 
swing  freely.  The  end  of  the  needle  which  takes  its  position 
toward  the  earth's  north  pole  is  called  the  north  pole  of  the 
needle;  the  opposite  end,  which  points  toward  the  south,  is  called 
the  south  pole  of  the  needle. 

If  a  magnetic  compass  is  placed  near  one  of  the  ends  of  a 
horseshoe  magnet,  the  compass  needle,  if  left  free  to  swing,  will 
take  a  position  with  one  end  pointing  more  or  less  directly  toward 
the  nearest  end  of  the  bent  bar.  For  convenience,  it  will  be 
assumed  that  the  north  pole  of  the  compass  needle  points  toward 
the  nearest  end  of  the  bent  bar.  Then,  if  the  compass  is  moved 
to  a  new  position  so  as  to  bring  it  near  the  other  end  of  the  bent 
bar,  the  needle  will  swing  on  its  pivot  so  that  the  south  pole  of 
the  needle  will  point  more  or  less  directly  toward  the  nearest  end 
of  the  bent  bar.  If  the  compass  is  repeatedly  moved  away  from 
the  bent-bar  magnet  and  brought  back  near  it  as  just  described, 
the  north  pole  of  the  needle  will  always  be  attracted  by  and 
point  toward  the  same  end  of  the  bent  bar,  and  the  south  pole 
will  always  behave  in  the  same  manner  relative  to  the  other  pole 
of  the  bent  bar. 

In  the  horseshoe  magnet,  the  bar-end  which  attracts  the  north 
pole  of  the  compass  needle  is  called  the  south  pole  of  the  horseshoe 
magnet ;  and  the  bar-end  which  always  attracts  the  south  pole 
of  the  needle  is  called  the  north  pole  of  the  horseshoe  magnet. 

The  letters  N  and  S  are  customarily  used  to  designate  the 
north  and  south  poles  respectively  of  a  magnet. 

If  the  compass  is  placed  immediately  between  the  bar-ends  of 
the  horseshoe  magnet,  the  needle  will  take  a  position  straight 
across  between  the  poles,  with  the  north  pole  pointing  toward 
the  south  pole  of  the  horseshoe  magnet,  and  its  south  pole 
pomting  toward  the  north  pole  of  the  horseshoe  magnet. 


6  ELECTRIC  IGNITION 

6.  Magnetic  Field.  —  The  region  throughout  which  a  magnet 
acts  to  attract  pieces  of  iron  and  steel  is  called  the  "  magnetic 
field "  of  the  magnet.     The  magnetic  field  has  its  greatest 
strength  near  the  ends,  or  poles,  of  the  magnet,  and  is  especially 
strong  in  the  space  between  the  ends  of  the  horseshoe  magnet. 
The  magnetic  field  is  said  to  be  permeated  with  "  magnetic  lines 
of  force."     The  position  which  a  very  small  compass  needle 
takes  when  placed  in  the  magnetic  field  of  a  relatively  large 
magnet  indicates  with  fair  accuracy  the  direction  of  the  lines 
of  force  in  the  locality  occupied  by  the  compass  needle.     The 
length  of  the  needle  approximately  coincides  with  the  direction 
of  the  lines  of  force.     The  needle  must  of  course  be  free  to  swing. 

If  the  north  pole  of  a  long,  thin  magnetic  needle  is  placed 
between  the  poles  of  a  horseshoe  magnet,  the  magnetic  force 
tends  to  move  the  needle  pole  in  the  direction  from  the  north 
pole  of  the  horseshoe  magnet  toward  the  south  pole  of  the  horse- 
shoe magnet,  which  is  the  direction  in  which  the  lines  of  force 
act  in  that  locality.  If  the  north  pole  of  the  needle  is  placed  in 
any  other  part  of  the  magnetic  field  of  the  horseshoe  magnet, 
the  magnetic  force  of  the  latter  also  tends  to  move  the  needle 
pole  in  the  direction  of  the  lines  of  force  at  the  needle  pole,  and 
to  carry  it  along  the  same  lines  of  force  in  the  direction  from  the 
north  pole  to  the  south  pole  of  the  horseshoe  magnet.  The 
path  which  the  needle  pole  will  follow  may  be  a  very  indirect 
one  of  a  circuitous  nature. 

It  is  customary  to  assume  that  there  is  a  flow  of  magnetism, 
called  magnetic  flux,  in  the  magnetic  field  from  the  north  pole 
to  the  south  pole  of  a  magnet,  the  flux  at  any  point  being  in  the 
direction  in  which  the  magnetic  force  tends  to  move  a  magnetic 
north  pole.  The  complete  magnetic  circuit  through  which  the 
flux  occurs  includes  the  length  of  the  steel  bar  from  end  to  end. 

7.  Magnet  Keeper  and  Its  Effect.  — A  magnet  keeper  of  soft 
iron  or  soft  (mild)  steel  is  generally  provided  with  a  horseshoe 
magnet.     In  Fig.  2  such  a  keeper  A  is  shown  in  place  across  the 
ends  of  the  magnet  bar.     The  purpose  of  the  keeper  is  to  prevent 
the  magnet  from  losing  its  magnetism. 

When  the  space  between  the  poles  of  the  magnet  is  bridged  by 


INTRODUCTORY  7 

the  keeper  as  shown  in  the  figure,  the  magnet  will  not  attract 
pieces  of  iron  and  steel  with  nearly  as  much  force  as  when  the' 
keeper  is  not  in  place.  The  keeper  has  a  similar  effect,  and  to 
practically  the  same  extent,  if  laid  against  the  sides  of  the  bent 
bar  so  as  to  bridge  the  space  between  the  poles  of  the  magnet. 
Or  the  keeper  may  be  made  so  as  to  fit  between  the  ends  of  the 
bar  as  shown  in  Fig.  3,  and  will  then  also  have  the  effect  of  weak- 
ening the  magnetic  field  in  the  manner  described. 

The  weakening  of  the  magnetic  field  by  the  keeper  is  more 
complete  when  the  keeper  fits  accurately  against  the  magnet  so 
that  there  is  a  large  area  of  metallic  contact  between  them,  than 
when  the  surfaces  that  touch  each  other  are  rough  and  make  but 
imperfect  contact. 

The  keeper  offers  an  easier  path  for  the  magnetic  flux  than 
is  offered  by  air,  therefore  nearly  all  of  the  flux  is  through  the 
keeper,  only  a  small  proportion  passing  through  the  air. 

The  magnetic  flux  through  the  bent  bar  of  the  magnet  is  not 
decreased  by  bridging  the  space  between  the  poles  with  the 
keeper,  but,  on  the  contrary,  a  large  increase  of  flux  through  the 
magnet  bar  is  caused  by  putting  the  keeper  in  place.  Proof  of 
the  last  statement  will  appear  in  connection  with  the  method  of 
operating  one  of  the  various  types  of  magnetos  for  generating 
electricity. 

8.  Magnetic  and  Non-magnetic  Materials.  —  Iron  and  alloys 
containing  a  large  proportion  of  iron  are  the  only  materials  that 
are  magnetic  to  an  appreciable  extent.  Steel  is  a  combination, 
or  an  alloy,  of  chemically  pure  iron  (ferrum)  with  other  chemical 
elements. 

Except  iron  and  steel,  all  of  the  materials  ordinarily  used  in 
machinery  and  electrical  apparatus  are  either  non-magnetic,  or 
magnetic  to  only  such  a  slight  extent,  compared  with  commercial 
iron  and  steel,  that  they  can  be  considered  non-magnetic  for  the 
present  purpose.  These  non-magnetic  materials  include  brass, 
bronze,  aluminum,  aluminum  alloys  generally,  zinc,  porcelain, 
steatite  (soapstone),  glass,  mica,  rubber,  pitch,  dry  wood,  wood 
fiber,  cotton,  silk,  hemp,  flax,  and  paper. 

Strictly  non-magnetic  materials  are  not  attracted  by  a  magnet. 


8 


ELECTRIC  IGNITION 


The  magnetic  field  is  not  affected  by  their  presence.  If  a  piece 
of  non-magnetic  material  is  placed  so  as  to  bridge  the  air  gap 
between  the  poles  of  a  magnet  after  the  manner  of  using  a  magnet 
keeper,  no  appreciable  change  will  be  produced  in  the  magnetic 
field. 

9.  Compound  or  Composite  Magnets.  —  The  permanent  mag- 
nets used  in  magnetos  for  generating  electricity  for  ignition  pur- 
poses are  generally  made  up  of  several 
bar  magnets  bent  into  the  shape  of  the 
letter  U  and  grouped  closely  together. 
Fig.  4  shows  a  method  of  grouping  the 
individual  magnets  together  that  is  very 
commonly  used  for  forming  a  composite 
magnet.  The  north  poles  of  all  the  indi- 
vidual magnets  are  placed  together,  and 
likewise  the  south  poles. 

Rectangular  bars  bent  flatwise  as  shown 
are  very  generally  used,  but  other  forms 
of  steel  bars,  including  round  ones,  are 
also  used  to  some  extent.  The  reason  for 
using  composite  magnets  is  that  it  is  dif- 
ficult, in  fact  practically  impossible,  to 
make  magnets  of  one  piece  sufficiently 
large  for  magnetos  to  be  used  for  ignition  purposes. 


FIG.  4. 

Compound  or  Composite 
Magnet. 


Principle  of  Electric  Generators. 

10.  In  all  power-driven  electric  generators  the  generation  of 
electricity  is  due  to  directly  and  repeatedly  varying  the  number 
of  lines  of  magnetic  force  that  pass  through  the  opening  of  a  coil 
of  wire  (not  through  the  length  of  the  wire  itself).  This  varia- 
tion generally  includes  reversing  the  direction  of  magnetic  flux 
through  the  coil  opening,  although  in  some  unusual  designs  the 
magnetic  flux  is  not  reversed  in  direction  through  the  coil  open- 
ing. Varying  the  number  of  lines  of  magnetism  through  the 
coil  of  wire  induces  an  electromotive  force  in  the  wire,  which 
tends  to  cause  a  flow  of  electricity  through  the  wire  and  also 


INTRODUCTORY  9 

through  whatever  apparatus  may  be  suitably  connected  to  the 
wire. 

The  electromotive  force  is  induced  in  the  coil  only  during  the 
time  of  variation  in  the  amount  of  magnetic  flux  through  the  coil. 
A  constant  flux  of  magnetism  through  a  coil,  without  change  in 
the  number  of  lines  of  magnetic  force  passing  through  the  coil 
opening,  does  not  induce  an  electromotive  force  in  the  coil. 

The  methods  by  which  the  number  of  lines  of  force  passing 
through  a  coil  are  made  to  vary  are  numerous.  They  come 
under  two  general  methods,  however.  In  one  of  these  general 
methods  the  wires  of  the  coil  are  caused  to  cut  through  the  lines 
of  magnetic  force  in  such  a  manner  as  to  vary  the  number  of 
lines  of  force  passing  through  the  coil.  In  the  other  general 
method  the  magnetic  flux  through  a  bar  which  the  coil  encircles 
is  caused  to  vary  in  intensity,  also  generally  reverse,  without  the 
wires  of  the  coil  cutting  through  any  of  the  lines  offeree.  The 
more  important  ways  in  which  the  variation  of  magnetic  flux 
through  a  coil  is  accomplished  will  appear  in  the  descriptions 
of  various  types  of  generators  used  in  connection  with  electric 
ignition. 

11.  The  armature  of  an  electric  generator  consists  of  a  coil, 
or  coils,  of  wire  over  or  around  a  core,  or  cores,  of  magnetic 
material  which  is  not  a  permanent  magnet.  In  the  more  usual 
forms  of  generators  for  electric  purposes,  the  armature  rotates 
relative  to  the  magnets.  In  less  usual  forms,  the  armature 
remains  stationary  with  regard  to  the  magnets.  In  the  latter 
form  there  is  a  rotor  (rotating  part)  of  soft  iron  or  mild  steel, 
called  an  inductor.  In  both  cases  the  rotation,  or  oscillation,  of 
the  rotor  (armature  or  inductor)  causes  a  variation  in  the  num- 
ber of  the  lines  of  force  passing  through  the  opening  of  the  arm- 
ature coil,  and  thus  induces  an  electromotive  force  in  the  coil  of 
the  armature,  so  that  the  coil  will  deliver  current  when  the  elec- 
tric circuit  is  properly  closed,  as  through  the  other  apparatus  of 
an  ignition  system. 


CHAPTER  II. 

LOW-TENSION  ALTERNATING-CURRENT  MAGNETOS  WITH 
SINGLE- WOUND   SHUTTLE  ARMATURES. 

12.   The  field-magnets  of  a  magneto  are  shown  in  Fig.  5.     The 
field  magnet  is  composite,  being  made  up  of  six  individual  magnets 

in  pairs,  each  pair  consisting  of  a 
large  magnet  fitted  over  a  small 
one. 

Two  pole-pieces,  or  pole-shoes, 
of  mild  steel  or  cast-iron,  are  fast- 
ened opposite  each  other  and 
against  the  inner  surfaces  of  the 
inside  individual  magnets  by 
means  of  screws  which  pass  through 
the  magnets  into  threaded  holes  in 
the  pole -pieces. 

The  space  between  the  extreme 
ends  of  the  magnets  is  bridged  by 
a  piece  of  non-magnetic  metal, 
such  as  brass  or  aluminum  alloy, 
which  forms  a  base  for  the  mag- 
netic field  and  is  fastened  to  the 
Field-Magnets  and  Pole-Pieces  of  a  pole-pieces  by  screws,  one  of  which 

is  shown  partly  removed  beneath 

the  base.  The  opposite  faces  of  the  pole-pieces  are  bored  out 
cylindrical,  so  as  to  fit  close  to  the  armature,  or.  inductor, 
which  rotates,  or  oscillates,  between  them  when  the  machine 
is  operating.  The  ends  of  the  pole -pieces  are  slightly  counter- 
bored  to  receive  an  end-plate  (not  shown)  and  hold  it  con- 
centric with  the  bore  of  the  pole -pieces.  The  use  of  the 
end-plate  is  to  support  the  armature  and  other  parts,  as  will 
appear  later. 


FIG.  5. 


10 


ALTERNATING-CURRENT  MAGNETOS 


II 


13.  Abutted  Magnets.  —  Another  arrangement  of  the  field- 
magnets  is  shown  in  Fig.  6.  The  magnets  are  placed  on  opposite 
sides  of  the  armature  space  with  their  ends  against  each  other 
so  that  the  north  poles  are  together  and  have  one  of  the  pole- 


N    |   N 


s  I  s 


FIG.  6. 
Abutted  Field-Magnets  of  a  Magneto. 

pieces  fastened  to  them.  The  south  poles  are  also  together  and 
have  the  other  pole-piece  fastened  to  them.  Composite  magnets 
can  be  used  in  this  arrangement  as  well  as  that  shown  in  the 
preceding  figure. 

Rotary  Armature  Types. 

14.   An  armature  suitable  for  rotating  between  the  pole-pieces 
of  the  magnets  just  described  is  shown  in  Fig.  7.     The  general 


82- 


FIG.  7. 
Armature  of  an  Alternating-current  Electric  Generator.     Shuttle-wound  Type. 

nature  of  the  construction  of  the  armature  can  be  seen  by  referring 
to  Figs.  8,  9,  and  10. 

The  core  of  the  armature  has  the  general  form  shown  in  Fig.  8. 
It  is  made  of  mild  steel  or  very  pure  and  soft  iron  machined  so 
that  the  crowned  surfaces  have  a  cylindrical  form  to  fit  between 
the  pole-pieces.  The  crowned  surfaces  should  fit  as  close  as 


12 


ELECTRIC  IGNITION 


possible  to  the  pole-pieces  without  touching  them,  in  order  to 
make  the  air-gap  between  the  armature  and  pole-pieces  as  small 
as  possible. 

The  armature  winding  is  a  coil  of  wire  wound  around  the  neck 
which  lies  between  the  crowned  sides  of  the  core.  Fig.  9  shows 
the  core  with  part  of  one  layer  of  winding  in  place.  The  neck 
and  sides  of  the  space  in  which  the  coil  is  wound  are  first  cov- 


FIG.  8. 
Core  of  Shuttle-wound  Armature. 


FIG.  9. 
Partly  Wound  Armature  of  the  Shuttle  Type. 


FIG.  10. 
Elements  of  Shuttle-wound  Armature. 

ered  with  some  insulating  material,  such  as  silk  or  paper  that 
has  been  oiled  or  varnished,  mica,  or  wood  fiber  cut  from  sheets 
or  molded  to  form.  The  insulating  material  does  not  allow 
electricity  to  flow  through  it  in  appreciable  quantity.  A  side 
piece  of  insulation  is  shown  at  i  in  Fig.  9.  Copper  wire,  covered 
with  cotton  or  silk  thread  wound  around  it  so  as  to  form  an 
insulating  covering,  is  used  ordinarily.  In  the  better  class  of 
work,  the  wire  is  covered  with  two  windings  of  silk  or  cotton, 
one  winding  on  top  of  the  other.  The  wire  used  in  magneto 


ALTERNATING-CURRENT  MAGNETOS  13 

armatures  is  commercially  known  as  armature  wire  or  magnet 
wire,  single-covered  or  double-covered,  as  the  case  may  be  with 
regard  to  whether  there  is  one  or  two  layers  of  thread  wound 
on  it. 

One  end  of  the  wire  is  bare  and  fastened  to  the  metal  of  the 
armature  core  at  2,  so  that  the  copper  of  the  wire  and  the  metal 
of  the  core  are  in  metallic  (electric)  connection.  The  rest  of  the 
wire  is  carefully  insulated  from  the  core,  and  the  different  layers 
of  the  coil  are  also  carefully  insulated  from  each  other.  The 
wire-end  3  is  intended  to  represent  where  the  wire  has  been  cut 
off  before  the  first  layer  of  winding  was  completed,  in  order  to 
show  the  nature  of  the  winding. 

After  the  first  layer  of  the  winding  is  complete,  the  second 
layer  is  wound  over  it,  and  so  on,  layer  upon  layer,  till  the  wind- 
ing is  complete.  There  is  one  continuous  winding  throughout 
all  of  the  layers.  Some  insulating  material,  such  as  heavy  paper 
or  cloth,  is  generally  placed  between  the  layers,  especially  at 
the  bends  of  the  wire,  as  a  protection  to  the  silk  or  cotton  wrap- 
ping of  the  wire,  and  to  make  the  insulation  more  perfect  between 
the  layers. 

The  coil  is  then  wrapped  with  insulating  tape  and  bound 
around  circumferentially  of  the  core  with  bare  non-magnetic 
wire,  as  shown  in  Fig.  7.  The  tape  is  generally  of  cotton  or  linen 
web  saturated  with  insulating  varnish.  Liquid  varnish  is  also 
generally  applied  to  the  tape  while  wrapping  it  over  the  coil. 
The  varnish  is  waterproof  if  the  magneto  is  to  be  used  where 
there  is  any  likelihood  of  water  reaching  it.  It  is  better  for  it 
to  be  waterproof  so  as  to  exclude  atmospheric  moisture  even  if 
it  is  intended  to  be  used  only  in  places  free  from  water.  Brass 
or  bronze  wire  is  generally  used  for  the  circumferential  bands. 

A  disk-shaped  head  of  non-magnetic  material  is  fastened  to 
each  end  of  the  armature  core  after  the  winding  is  completed. 
Brass,  bronze,  or  aluminum  alloy  is  generally  used  for  these  heads. 
Each  head  carries  a  spindle  which  projects  outward  from  the 
winding.  The  spindles  are  usually  made  of  steel.  They  run  in 
suitable  bearings  during  the  rotation,  or  oscillation,  of  the  arma- 
ture while  the  magneto  is  operating. 


ELECTRIC  IGNITION 


One  of  the  spindles  shown  in  Fig.  10  is  hollow.  The  outer  end 
of  the  armature  wire  passes  through  the  hole  so  that  its  end 
projects  beyond  the  spindle  at  i .  Carrying  an  end  of  the  arma- 
ture winding  out  through  a  hollow  spindle  is  very  commonly 
used  in  magnetos  intended  for  ignition  purposes,  although  the 
wire  itself  is  not  generally  carried  through  the  spindle.  It  is 
more  usual  to  connect  the  armature  wire  to  a  rod  or  screw  which 
extends  through  the  hole  and  is  insulated  from  the  metal  of  the 
spindle  either  by  a  tube  of  hard  rubber  or  vulcanized  fiber,  a 
wrapping  of  sheet  mica,  or  some  other  suitable  means  of  insulation. 
An  armature  with  a  core  of  the  shape  shown  in  Fig.  8,  and 
wound  as  just  described,  is  called  either  an  I-armature,  an  H- 

armature,  or  a  shuttle- wound  armature. 
The  latter  name  is  on  account  of  the 
resemblance  of  the  armature  in  general 
appearance  to  the  shuttle  of  a  weaving 
loom.  The  names  I-armature  and 
H-armature  come  from  the  resemblance 
of  the  core,  when  looked  at  endwise,  to 
either  the  letter  I  or  the  letter  H,  ac- 
cording to  whether  the  core  is  held,  or 
lies,  with  the  crowned  surfaces  at  the 
top  and  bottom,  or  at  the  sides. 

15.   Electric    Arc   from    a    Shuttle- 
wound  Armature.  —  Fig.  u   shows  a 
shuttle- wound  armature  in  place  be- 
tween the  pole -pieces   of    permanent 
field-magnets.     The  armature  is  of  the 
Field-Magnets  and  Armature  of  general  form  of  that  shown  in  Figs.  7 
Magneto  with   Device    for  an(j  IO<     T^  bare  end  i  of  the  copper 

Showing  Positions  of  Arma-  r  ,-,  •     -,. 

ture  for  Maximum  Electric  Wlfe  °f  the  armature  wmdlng  Pr°Jects 
Arc  or  Spark.  from  the  end  of  the  hollow  spindle,  part 

of  the  insulation  2  being  removed  to 

expose  the  wire.  A  cam-shaped  projection  3  is  shown  on  the 
forward  end  of  the  front  spindle.  A  cam  of  this  particular  form 
is  not  usual  in  commercial  magnetos,  but  is  added  here  to  facili- 
tate the  explanation  of  the  principle  of  operation  of  the  magneto. 


FIG.  ii. 


ALTERNATING-CURRENT  MAGNETOS  15 

A  bent  wire  4  is  shown  in  contact  with  the  bare  end  i  of  the 
armature  wire  and  also  in  contact  with  the  convex  surface  of 
the  cam  or  lug  3. 

If  the  armature  is  rotated  in  the  direction  indicated  by  the 
arrow  on  the  armature  head,  and  the  bent  wire  4  is  held  stationary 
in  the  position  shown,  so  as  to  have  rubbing  or  slipping  contact 
with  the  wire-end  i  and  cam  3,  then  when  the  bent  wire  snaps 
off  the  edge  of  the  cam  as  the  latter  rotates  with  the  armature, 
an  electric  arc  will  be  drawn  between  the  end  of  the  wire  and  the 
edge  of  the  cam  at  the  point  of  separation  of  the  two,  provided 
the  speed  of  rotation  is  sufficiently  high.  A  rotative  speed  of  30 
to  40  revolutions  per  minute  is  sufficient  to  draw  quite  a  large 
arc  in  some  magnetos  when  the  parts  separate.  A  magneto  of 
the  size  commonly  used  on  portable  combustion  motors  will  give 
a  large  arc  when  the  armature  is  twirled  around  through  one  or 
two  revolutions  by  grasping  the  spindle  in  the  fingers ;  half  a  rev- 
olution caused  in  this  manner  will  give  a  good-sized  arc  in  some 
low- tension  magnetos  for  ignition. 

If  while  the  armature  is  rotating  at  a  speed  more  or  less  uni- 
form, the  bent  wire  4  is  swung  around  to  different  positions  but 
held  so  that  it  is  always  in  contact  with  both  the  wire-end  i  and 
the  cam  3  just  before  the  edge  of  the  latter  breaks  contact  with 
the  end  of  the  bent  wire,  it  will  be  found  that  while  a  good-sized 
arc  will  be  drawn  for  some  positions  of  the  bent  wire,  at  other 
positions  no  arc  whatever  will  appear  when  the  contact  is  broken. 
After  one  position  of  the  bent  wire  for  the  largest  electric  arc 
corresponding  to  the  speed  of  rotation  is  determined,  it  can  be 
seen,  by  swinging  the  bent  wire  slowly  around  the  axis  of  the 
rotating  spindle,  that  the  other  position  of  the  bent  wire  for 
maximum  arc  is  diametrically  opposite  the  position  first  deter- 
mined. In  other  words,  the  largest  arc  is  obtained  at  two 
positions  of  the  cam-edge  diametrically  opposite  each  other, 
which  may  be  expressed  by  saying  that  the  two  positions  of  the 
cam-edge  are  half  a  revolution  apart  for  maximum  electric  arcs. 

The  position  of  the  cam  at  any  instant  corresponds  of  course 
to  definite  positions  of  the  armature,  since  the  cam  and  armature 
are  rigidly  fastened  together. 


1 6  ELECTRIC  IGNITION 

It  can  also  be  seen,  by  the  same  process  as  just  described,  that 
the  two  positions  of  the  bent  wire  at  which  no  arc  is  obtained 
lie  midway,  or  approximately  midway,  between  the  positions  for 
maximum  arcs.  The  two  positions  for  no  arc  are  also  diametri- 
cally opposite  each  other,  and  therefore  half  a  revolution  apart. 

A  larger,  or  hotter,  arc  is  obtained  at  a  high  speed  of  rotation 
than  at  slow  speed. 

16.  Effect  of  Speed  of  Armature  on  Position  for  Maximum 
Arc.  —  If  the  positions  of  the  armature  for  maximum  arc  and 
no  arc  are  first  determined  as  above  while  the  armature  is  rotat- 
ing at  slow  speed,  say  50  revolutions  per  minute,  and  then  the 
armature  speed  is  increased  to  say  1 200  revolutions  per  minute, 
and  the  experiment  repeated,  it  will  be  found  that  the  bent  wire 
must  be  held  farther  around  in  the  direction  of  rotation  of  the 
armature  in  the  latter  case  in  order  to  obtain  the  maximum  arc 
and  no  arc.     This  means  that  the  maximum  arc  occurs  later  in 
the  revolution  of  the  armature  at  high  speed  than  at  low  speed, 
each  revolution  being  assumed  to  begin  at  the  same  position 
of  the  armature,  as  when  the  neck  of  its  core  is  in  a  vertical 
position.     The  cause  of  this  lag  in  the  time  of  production  of  the 
maximum  arc  will  be  explained  later. 

17.  Positions  of  Armature  for  Strong  Electric  Arc.  —  The  posi- 
tions of  the  armature  at  which  the  strongest  arc  can  be  obtained 
vary  with  variation  in  the  forms  of  the  pole-pieces  and  armature 
core,  as  well  as  with  the  speed  of  rotation,  as  has  been  mentioned. 
Most  magnetos  that  are  to  run  at  a  variable  speed  when  in 
service  are  generally  so  constructed  that  a  strong  arc  can  be 
produced  throughout  a  considerable  range  of  position  of  the  bent 
wire  applied  as  stated  above.     This  is  done  on  account  of  the 
advance  and  retard  of  ignition  relative  to  the  position  of  the 
pistons  of  the  motor,  as  well  as  on  account  of  the  lag  in  the  mag- 
neto with  regard  to  the  position  of  the  armature  at  the  instant 
of  maximum  arc.     The  lag  is  not  so  great  for  the  speed  usual 
for  combustion  motors  but  that  the  position  of  the  armature  for 
maximum  arc  can  be  pointed  out  in  a  general  way,  as  in  the 
following  paragraphs. 

Fig.  1 2  shows  conventionally  the  pole-pieces  and  shuttle-wound 


ALTERNATING-CURRENT  MAGNETOS 


armature  of  a  magneto.  A  double,  or  two-lobed,  cam  is  shown 
fastened  to  the  armature  spindle.  A  bent  wire  for  making  electric 
connection  between  the  cam  and  the  bare  projecting  end  of  the 
armature  wire  is  also  shown  in  place.  The  two  lobes  of  the  cam 
are  diametrically  opposite  each  other  and  are  in  such  positions 
relative  to  the  core  of  the  armature  that  if  a  line  were  drawn 


FIG.  12. 

Positions  of  Armature  for  Maximum  Electric  Arc  or  Spark.     Approximate. 

through  the  two  cam-edges  at  which  the  contact  with  the  bent 
wire  is  broken  as  the  armature  rotates,  the  line  would  be  parallel 
to  the  neck  which  connects  the  two  crowned  parts  of  the  core. 


FIG.  13. 
Positions  of  Armature  for  No  Electric  Arc  or  Spark.     Approximate. 

The  bent  wire  is  held  so  as  to  break  connection  with  the  cam- 
edge  which  is  uppermost  just  as  the  armature  core  passes  through 
its  upright  position  in  which  its  end  view  resembles  the  letter  I. 
The  arrow  indicating  the  direction  of  rotation  of  the  armature 
may  be  taken  as  cut  into  the  metal  of  the  core  so  that  it  rotates 
with  the  core. 

If  the  armature  is  rotating  at  a  very  slow  speed,  the  maximum 
electric  arc  for  that  speed  will  be  obtained  by  breaking  the  cir- 
cuit while  the  armature  is  passing  through  the  vertical  positions 


i8 


ELECTRIC  IGNITION 


shown  in  Fig.  12,  or  while  it  is  passing  through  positions  very 
near  the  vertical.  The  maximum  spark  will  occur  twice  during 
each  revolution. 

The  positions  of  no  spark  are  shown  in  Fig.  13.  The  neck  of 
the  armature  core  is  horizontal,  or  nearly  so,  in  these  positions, 
so  that  the  end  view  of  the  core  resembles  the  letter  H. 


FIG.  14. 
Maximum-spark  Positions  of  Armature. 

If  the  armature  is  rotated  at  a  speed  as  high  as  1200  revolu- 
tions per  minute,  then  its  positions  of  maximum  arc  will  be  some- 
what as  indicated  in  Fig.  14,  which  positions  are  somewhat  later 


FIG.  15. 
Sparkless  Positions  of  Armature. 

in  the  revolution  than  for  slow  speed  of  rotation.  The  positions 
of  no  spark  at  high  speed  will  be  somewhat  as  shown  in  Fig.  15. 
18.  Laminated  Armature  Core.  —  The  rotation  of  the  arma- 
ture in  the  magnetic  field  induces  electric  currents,  called  fou- 
cault  currents,  in  the  armature,  as  well  as  current  in  the  winding 
of  the  armature.  If  the  core  is  made  of  one  solid  piece  of  steel 
or  iron,  the  foucault  currents  in  it  cause  it  to  heat  and  are  other- 
wise objectionable.  In  order  to  keep  this  objectionable  action 
as  small  as  possible,  it  is  common  practice  to  build  up  the  core 


ALTERNATING-CURRENT  MAGNETOS  19 

from  thin  sheet  steel  cut  into  I-shaped  pieces.  The  steel  used 
for  these  pieces  is  commercially  known  as  armature  steel.  The 
pieces  are  generally  cut  out  by  a  stamping  press. 

Fig.  1 6  shows  a  laminated  armature  core  built  up  in  this 
manner.  The  "  disks,"  or  laminations,  are  sometimes  separated 
from  each  other  by  some  such  material  as  silk  fabric  or  thin  sheet 
paper  properly  prepared  by  oiling  or  varnishing;  in  other  cases, 


FIG.  16. 
Laminated  Core  of  Shuttle  Armature. 

varnish  or  the  black  scale  on  the  surface  of  the  steel  is  depended 
on  as  sufficient  insulation.  The  sheet  steel  from  which  the  disks 
are  cut  is  of  about  the  thickness  of  that  used  for  stovepipes. 

The  armature  disks  are  pressed  together  under  heavy  pressure, 
as  that  of  a  hydraulic  press,  after  they  have  been  grouped  to 
form  the  core.  They  are  then  fastened  together  by  rivets  or 
other  suitable  means. 

19.  Magnetic  Flux  in  a  Rotating  I-shaped  Armature  Core. — 
It  has  been  stated  that  the  electromotive  force  and  current  in 
the  winding  of  an  armature  are  induced  by  changing  the  amount 
of  magnetic  flux  through  the  space  surrounded  by  the  coil.  In 
the  shuttle-wound  armature  the  variation  of  magnetic  flux 
occurs  in  the  steel  neck  of  the  core  on  which  the  insulated  wire 
is  wound. 

Fig.  17  shows  the  general  nature  of  the  magnetic  flux  through 
an  I-shaped  magnetic  core  during  the  time  it  is  rotating  between 
the  pole-pieces  of  the  magnets.  Only  the  end  views  of  the  core 
and  pole -pieces  are  shown  in  the  figure.  The  pole-pieces  are 
marked  N  and  S  to  indicate  the  north  and  south  poles  respec- 
tively. The  letter  and  the  feathered  arrow  indicating  the  direc- 


20 


ELECTRIC   IGNITION 


(a) 


FIG.  17. 
Magnetic  Flux  through  Shuttle  Armature  Core  in  Different  Positions. 


ALTERNATING-CURRENT  MAGNETOS 


21 


FIG.  17  (continued). 
Magnetic  Flux  through  Shuttle  Armature  Core  in  Different  Positions. 

tion  of  rotation  of  the  core  may  be  considered  as  cut  into  the 
metal  of  the  core. 

In  (a)  the  core  is  in  the  H  position  and  the  magnetic  flux 
through  it  is  from  N  to  5,  as  indicated  by  the  lines  with  arrow 
heads  along  them.  This  is  one  of  the  positions  of  the  core  in 
which  the  greatest  amount  of  magnetic  flux  occurs  through  the 
neck  that  connects  the  crowned  ends  of  the  core.  When  the  core 
has  been  rotated  to  the  position  (b)  there  is  less  flux  through  it, 
because  less  of  the  crowned  ends,  or  sides,  is  opposite  the  pole- 
pieces.  The  direction  of  flux  for  this  position  is  in  general  as  in- 
dicated by  the  arrow-headed  lines.  When  the  core  is  in  position 
(c)  there  is  very  little  flux  through  it,  because  the  crowned  surfaces 
have  almost  entirely  moved  away  from  opposite  the  pole-pieces. 

In  the  vertical  position  of  the  core,  as  shown  in  (d),  there  is 
no  longer  any  magnetic  flux  through  the  core -neck  around  which 
the  coil  is  wound  in  the  complete  armature.  In  other  words, 
the  magnetic  flux  through  the  coil  is  of  zero  value  when  the  core 
is  in  the  I  position.  There  is  some  flux  through  the  crowned 


22  ELECTRIC  IGNITION 

ends  of  the  core,  however,  from  pole  to  pole,  as  indicated  by  the 
arrow-headed  lines;  but  this  has  no  effect  to  produce  electro- 
motive force  and  current  in  the  armature  winding. 

In  position  (e)  the  magnetic  flux  through  the  core -neck  is  in 
the  opposite  direction  from  that  in  the  first  three  positions,  but 
the  flux  is  from  the  N  pole  to  the  S  pole,  as  it  always  is. 

In  the  first  three  positions  the  flux  is  through  the  core  from 
the  arrow-marked  side  toward  the  blank  side,  but  in  position 
(e)  the  flux  is  from  the  blank  side  toward  the  arrow-marked  side 
of  the  core,  as  is  also  the  case  in  positions  (/)  and  (g).  In  the 
latter  position  the  flux  is  again  a  maximum  of  the  same  value 
as  for  position  (a),  but  in  the  opposite  direction  through  the  core. 

In  positions  (g),  (ti),  (i),  (&),  and  (/)  the  paths  of  flux  are  similar 
respectively  to  those  in  (a),  (£>),  (c),  (e),  and  (/),  but  the  flux  is 
in  the  opposite  direction  through  the  core -neck  on  account  of 
the  core  being  half  a  revolution  further  around  in  the  positions 
(h)  to  (/)  than  in  (b)  to  (/).  In  position  (j)  there  is  no  flux  through 
the  core-neck,  but  the  flux  through  the  crowned  sides  of  the  core 
is  in  the  opposite  direction  from  what  it  was  in  (d),  on  account 
of  a  difference  of  half  a  revolution  between  the  two  positions. 

Fig.  1 8  is  a  diagram  representing  the  relative  amounts  of 
magnetic  flux  through  the  core -neck  of  an  H-armature  for  all  of 
its  positions  during  one-half  a  revolution.  The  distance  from 
•O  vertically  up  to  the  curve  is  the  amount  of  flux  when  the  core 
is  stationary  in  the  position  shown  in  Fig.  17  at  (a).  The  vertical 
distance  B,  Fig.  18,  is  the  flux  when  the  core  has  been  rotated 
45  degrees  to  the  position  in  Fig.  17  at  (&).  At  Z>,  where  the 
curve  crosses  the  zero  line,  there  is  no  flux  through  the  core -neck. 
This  corresponds  to  position  (d)  in  Fig.  17.  When  the  armature 
is  in  position  (/),  three-quarters  of  a  revolution  from  the  starting 
position,  the  flux  is  equal  to  that  for  position  (b)  but  in  the 
opposite  direction.  This  is  indicated  in  the  diagram  by  taking 
the  distance  F  below  the  zero  line. 

When  the  core  is  rotating  at  a  very  slow  but  uniform  speed, 
the  rate  of  change  in  the  magnetic  flux  through  the  core -neck  is 
more  rapid  while  the  core  is  passing  from  position  (c)  to  position 
(e),  and  from  position  (i)  to  position  (&),  than  during  the  other 


ALTERNATING-CURRENT  MAGNETOS 


portions  of  the  revolution.  (The  reason  for  limiting  this  and 
the  following  statement  to  slow  speed  will  appear  later.)  While 
the  core  is  passing  through  positions  at  and  near  those  shown  in 
(a)  and  (g),  the  rate  of  change  in  magnetic  flux  through  the  core 
is  very  low  compared  with  the  rate  for  the  movements  just 
mentioned.  In  one  position  at  or  near  (a),  and  another  at  or 


Zero  Line 
J£  Revolution- 


FIG.  i 8. 

Graph  Showing  Magnetic  Flux  in 
Shuttle  Armature. 


FIG.  19. 

Graph   Showing   Rate   of   Variation   of 
Magnetic  Flux  in  Shuttle  Armature. 


near  (g),  the  rate  of  change  falls  to  zero.     This  is  when  the  flux 
stops  decreasing  and  just  before  it  begins  increasing. 

As  the  armature  core  moves  from  position  (c)  to  position  (e), 
the  decrease  first  occurs  in  the  flux  through  the  core -neck,  fol- 
lowed by  reversal  and  increase  of  flux  in  the  opposite  direction 
through  the  core-neck.  These  are  together  equivalent  to  a 
continuous  decrease  of  magnetic  flux.  The  same  is  true  for 
the  movement  from  position  (i)  to  position  (&).* 

*  This  may  possibly  be  more  readily  understood  by  considering  a  somewhat 
analogous  case  in  the  flow  of  water,  as  follows:  If  two  pipes  are  delivering  water 
into  a  reservoir  at  the  same  time,  a  large  pipe  at  the  rate  of  50  gallons  per  minute, 


24  ELECTRIC  IGNITION 

Fig.  19  shows  the  rate  of  change  of  magnetic  flux  through  the 
core-neck  for  all  positions  of  the  core  during  one-half  a  revolu- 
tion, starting  from  position  (a),  Fig.  17.  The  vertical  distance 
C,  Fig.  19,  represents  the  rate  of  change  of  flux  while  the  arma- 
ture is  passing  through  the  position  shown  at  (c),  Fig.  17.  The 
rate  of  change  for  position  (e)  in  the  latter  figure  is  shown  as 
the  vertical  distance  E,  Fig.  19.  If  the  curve  were  given  for  the 
second  half -re  volution,  it  would  be  below  the  zero  line,  since  the 
increase  and  decrease  take  place  in  opposite  directions  through 
the  core-neck  from  what  they  do  in  the  first  half -revolution. 

20.  Electromotive  Force  and  Current  Induced.  —  If  a  coil  of 
insulated  wire  is  wound  around  the  core-neck,  as  in  Fig.  20,  so 
as  to  form  an  armature,  an  electromotive  force  is  induced  in  the 
coil  while  the  armature  is  rotating  in  the  magnetic  field  between 
the  pole-pieces  of  the  magnets.     This  electromotive  force  is  pro- 
portional, or  nearly  so,  to  the  rate  of  change  of  the  magnetic  flux 
through  the  core-neck.     (A  steady  flux  of  magnetism  of  constant 
amount  does  not  induce  an  electromotive  force.) 

If  the  electric  circuit  is  closed,  a  current  will  flow  through  the 
winding  whenever  there  is  an  electromotive  force.  In  the  figure 
a  complete  closed  electric  circuit  is  obtained  by  connecting  both 
ends  of  the  insulated  wire  to  the  metal  of  the  core.  These  con- 
nections are  indicated  by  black  spots  and  are  numbered  i  and  2. 

21.  Armature  Lag.  —  It  has  been  stated  that  the  maximum 
arc  is  obtained  later  in  the  revolution  of  the  armature  when  the 
speed  of  rotation  is  high  than  when  it  is  low,  and  that  this  is  due 
to  armature  lag. 

The  armature  lag  is  due  to  both  the  magnetic  lag  of  the  core 

and  a  small  pipe  at  the  rate  of  10  gallons  per  minute,  then  the  rate  of  increase  in 
the  amount  of  water  in  the  reservoir  is  50  +  10  =  60  gallons  per  minute.  If 
the  flow  of  the  small  pipe  is  stopped  and  another  pipe  opened  to  draw  water  from 
the  reservoir  at  the  rate  of  10  gallons  per  minute,  the  rate  of  increase  of  water  in 
the  reservoir  will  be  reduced  to  50  —  10  =  40  gallons  per  minute.  The  difference 
between  the  two  rates  of  increase  is  60  —  40  =  20  gallons  per  minute. 

An  analogous  case  is  that  of  first  flowing  water  into  a  tank  at  the  rate  of  10 
gallons  per  minute,  then  stopping  the  inflow  and  drawing  out  water  at  the  same 
rate.  Drawing  out  water  may  be  considered  as  a  negative  filling  of  the  tank. 
The  difference  between  the  two  rates  of  filling,  one  positive  and  the  other  negative, 
is  10  •+•  10  =  20  gallons  per  minute. 


ALTERNATING-CURRENT  MAGNETOS  25 

and  the  lag  of  the  current  behind  the  induced  electromotive  force. 
It  requires  an  appreciable  amount  of  time,  in  comparison  with 
the  speed  at  which  the  magneto  rotates  on  a  high-speed  multi- 
cylinder  motor,  to  change  the  rate  of  magnetic  flux  in  a  piece  of 
steel  or  iron.  And  the  electric  current  lags  slightly  behind  the 
electromotive  force  that  is  induced  by  the  change  of  magnetic 
flux.  The  current  lag  is  due  chiefly  to  the  action  of  the  current* 
in  each  turn  (or  single  wrap)  of  the  coil  winding  upon  the  cur- 
rent in  the  other  turns  of  the  winding,  and  to  the  reaction  of 
the  current  upon  the  magnetism  of  the  core.  These  and  other 
causes  together  produce  armature  reactance  and  lag. 

Referring  to  Fig.  17,  if  (a)  is  one  of  the  two  positions  of  the 
core  for  maximum  magnetic  flux  through  the  core -neck  when  the 
core  is  standing  still  or  rotating  at  very  slow  speed,  then  at  high 
speed  of  rotation  the  maximum  flux  will  occur  slightly  later  in 
the  revolution  of  the  core;  that  is,  after  the  core  has  passed 
slightly  beyond  the  position  shown  in  (a).  And  if  (d)  is  one  of 
the  positions  for  no  flux  through  the  core-neck  when  the  core  is 
not  rotating,  then  the  position  of  no  flux  through  the  core -neck 
will  be  somewhat  further  around  in  the  direction  of  rotation  at 
high  speed.  Thus,  position  (e)  may  be  the  position  of  no  flux 
through  the  core -neck  at  excessively  high  speed  of  rotation.  The 
same  applies  to  positions  (g),  (/'),  and  (k). 

The  reactions  in  the  armature  cause  the  maximum  current  to 
occur  somewhat  later  than  the  maximum  magnetic  flux,  as  has 
been  stated.* 

22.  Alternating  Current  Generated.  —  For  convenience  in  dis- 
cussing the  nature  of  the  current  generated  in  an  armature  wind- 
ing, it  will  first  be  assumed  that  there  is  no  lag  in  the  armature. 

Referring  to  Fig.  20,  (A)  is  one  of  the  positions  of  maximum 
magnetic  flux  through  the  core-neck  when  the  armature  is  stand- 
ing still,  and  also  when  it  is  rotating,  the  latter  in  accordance 
with  the  assumed  condition  of  no  lag.  As  the  armature  rotates 

*  It  is  not  thought  desirable  to  give  any  further  discussion  of  armature  react- 
ance and  lag  in  a  work  of  this  nature,  especially  as  it  is  very  probable  that  the 
largest,  or  hottest,  arc  is  obtained  by  breaking  the  electric  circuit  slightly  before 
the  armature  reaches  the  position  which  would  give  maximum  current  if  the  circuit 
were  left  closed. 


26 


ELECTRIC  IGNITION 


(A) 


zzQn 


/ 


CD) 


FIG.  20. 
Direction  of  Current  Flow  in  Winding  of  Shuttle  Armature. 


ALTERNATING-CURRENT  MAGNETOS 


•       (K)  (L) 

FIG.  20  (continued). 

Direction  of  Current  Flow  in  Winding  of  Shuttle  Armature. 

through  the  first  quarter-revolution  from  position  (A),  the  mag- 
netic flux  through  the  core-neck  decreases,  slowly  at  first,  and 
at  an  increasing  rate  till  the  armature  has  reached  position  (D) 
at  the  completion  of  the  quarter-revolution,  in  which  position 
there  is  no  magnetic  flux  through  the  core-neck.  The  decrease 
of  magnetic  flux  through  the  core-neck  causes  an  electric  current 
to  flow  through  the  insulated  wire  of  the  winding.  The  direc- 
tion of  flow  of  the  current  is  as  indicated  by  the  arrows  on  the 
wire.  The  path  of  the  current  is  from  2  through  the  length  of 
the  wire  to  i,  and  thence  through  the  metal  of  the  core  from 
i  to  2.  The  current,  beginning  at  zero  value,  keeps  increasing 
during  the  first  quarter-revolution  and  reaches  its  maximum 
value  in  position  (D).  From  position  (D)  to  position  (G)  the 
current  decreases  until  it  drops  to  zero  at  the  completion  of  the 
first  half -re  volution,  corresponding  to  position  (G). 
During  the  second  half -revolution,  from  (G)  to  (L),  a  similar 


28  ELECTRIC  IGNITION 

action  takes  place;  but,  since  the  coil  has  been  turned  over,  the 
direction  of  current  flow  through  the  wire  is  opposite  that  during 
the  first  half -revolution.  The  direction  of  current  flow  during 
the  second  half-revolution  is  indicated  by  the  arrows  on  the  wire 
in  (H)j  (7),  (/),  and  (K).  It  flows  through  the  wire  from  i  to  2. 

Briefly,  under  the  assumed  condition  of  no  lag,  starting  from 
position  (A),  the  current  increases  from  zero  to  its  maximum 
value  during  the  first  quarter-revolution,  and  decreases  to  zero  dur- 
ing the  second  quarter-revolution;  then  increases  to  a  maximum 
in  the  opposite  direction  during  the  third  quarter-revolution, 
and  decreases  to  zero  again  during  the  last  quarter-revolution. 
This  action  is  repeated  during  each  revolution.  The  speed  of 
rotation  has  been  assumed  to  be  constant. 

An  electric  current  of  the  nature  just  described  is  called  an 
alternating  current. 

The  lag  causes  the  maximum  current  to  occur  later  in  the 
rotation  of  the  armature  than  just  stated.  At  a  high  speed  of 
rotation  positions  (E)  and  (K)  may  be  those  for  maximum  cur- 
rent. Although  the  lag  is  very  small  as  measured  in  fractions 
of  a  second  of  time,  it  may  be  very  appreciable  when  measured 
in  parts  of  a  revolution  of  the  magneto.  Thus,  a  shuttle-wound 
magneto  that  is  igniting  a  six-cylinder  four-cycle  motor  runs  at 
1800  revolutions  per  minute  when  the  speed  of  the  motor  is  1200 
revolutions  per  minute.  The  current  must  rise  from  zero  to  its 
maximum  value  and  drop  back  to  zero  again  3600  times  per  min- 
ute, which  is  60  times  per  second.  The  current  has  ^o  of  a  second 
to  rise  to  its  maximum  and  drop  back  to  zero  again.  A  lag  of 
yAo  of  a  second  corresponds  to  3*0  of  a  revolution,  which  is  9 
degrees  of  angle. 

23.  Graphical  Representation  of  Current  in  a  Shuttle-wound 
Armature.  —  Fig.  21  shows  graphically  the  general  nature  of  the 
current  generated  in  a  shuttle-wound  armature.  The  revolu- 
tions of  the  armature  are  measured  horizontally,  and  the  amount 
of  current  is  measured  vertically.  The  rotation  is  measured 
from  the  position  in  which  the  magnetic  flux  through  the  core- 
neck  is  a  maximum  when  the  armature  is  not  rotating;  this  is 
position  (a)  in  Fig.  17,  and  position  (-4)  in  Fig,  20.  In  the  dia- 


ALTERNATING-CURRENT  MAGNETOS 


29 


gram,  Fig.  21,  the  point  of  zero  rotation  is  indicated  by  O.  It 
is  assumed  that  the  armature  rotates  at  a  uniform  speed.  The 
current  flow  is  represented  by  the  curved  line  ABODE. 

The  current  has  zero  value  at  A  after  the  armature  has  rotated 
through  a  small  angle.  The  current  increases  and  reaches  its 
maximum  value  at  B  slightly  after  the  completion  of  the  first 
quarter-revolution.  The  maximum  value  of  the  current  at  this 
point  is  BF.  Decrease  of  current  begins  at  B  and  continues  till 
zero  value  is  reached  again  at  C,  which  is  half  a  revolution  from 
A.  The  flow  of  current  then  begins  in  the  opposite  direction 


-One  Cycle  of  Current 
B 


— 1  Revolution  

FIGS.  21  and  22. 
Current  in  Armature  Winding  as  Affected  by  Different  Forms  of  Pole-pieces. 


and  increases  till  it  reaches  maximum  value  again  at  D,  slightly 
after  three-quarters  of  a  revolution.  This  may  be  called  a 
negative  maximum.  Its  value  is  DG.  Decrease  then  begins 
and  the  current  falls  to  zero  again  at  E,  just  after  the  completion 
of  the  revolution. 

24.  Cycle  of  Current.  —  The  series  of  changes  through  which 
the  current  repeatedly  passes  is  called  the  cycle  of  the  current. 
In  this  case  the  complete  cycle  is  passed  through  during  one 
revolution  of  the  armature. 

25.  Form  of  Current  Curve  is  Affected  by  Shape  of  Pole- 
Pieces.  —  The  shape  of  the  pole-pieces,  especially  at  the  edges, 


ELECTRIC  IGNITION 


or  lips,  determines  to  some  extent  the  form  of  the  current  curve. 
The  lips  of  the  pole-pieces  are  the  edges  i,  2,  3,  and  4  in  Fig.  17, 
view  (b). 

If  the  current  curve  in  Fig.  21  is  obtained  with  the  pole-piece 
lips  rounded  as  in  Fig.  17,  then  for  sharp-edged  lips  like  those 
in  Fig.  20  the  current  curve  will  be  flatter  and  broader  at  the 
top  and  bottom,  somewhat  as  shown  in  Fig.  22.  The  maximum 
current  is  not  so  great  in  the  latter  figure,  but  the  current  remains 
large  during  a  greater  part  of  a  revolution  than  in  Fig.  21. 

Two  forms  of  pole-pieces,  which  give  broad  peaks  of  the  nature 
of  those  at  b  and  d  in  Fig.  22,  are  shown  in  Fig.  23.  In  (A)  the 


(A)  (B) 

FIG.  23. 
Pole-pieces  with  Rounded  Lips  and  with  Tooth-shaped  Lips. 

middle  portions  of  the  lips  extend  out  farther  than  the  ends. 
In  (B)  one  lip  of  each  pole-piece  is  in  the  form  of  teeth  which 
resemble,  in  a  measure,  those  of  a  comb.  The  lips  with  teeth 
extend  out  farther  from  the  magnet  poles  than  those  which  have 
smooth  edges.  The  pole-pieces  in  (B)  are  for  an  armature  that 
rotates  clockwise,  so  that  the  surface  of  the  core  that  is  next  to 
the  pole-pieces  moves  away  from  the  pole-piece  lips  with  teeth 
toward  the  smooth-lipped  pole-pieces.  Pole-pieces  of  the  forms 
of  those  shown  in  Fig.  23  give  a  more  gradual  rate  of  change  in 
the  magnetic  flux  as  the  armature,  or  inductor,  rotates  than 
occurs  when  the  lips  are  straight  as  in  Fig.  17. 

26.  Position  of  Armature  for  Maximum  Arc.  —  In  accordance 
with  what  has  been  stated,  it  may  be  seen  that  in  a  magneto 
with  a  shuttle-wound  rotating  armature,  the  largest,  or  hottest, 
arc  is  obtained  by  breaking  the  electric  circuit  while  the  armature 
is  passing  through  a  position  near  that  in  which  the  crowned 


ALTERNATING-CURRENT  MAGNETOS 


31 


sides  of  the  core  span  the  space  between  the  lips  of  the  pole- 
pieces,  as  in  Fig.  20  at  (£)  and  (K). 

27.  A  low-tension  alternating-current  magneto  with  shuttle- 
wound  armature  is  shown  in  Fig.  24.  The  illustration  is  partly 
a  longitudinal  section  and  partly  full  view,  the  latter  being  mostly 
of  interior  parts. 

The  beginning  of  the  armature  winding  is  connected  to  the 
armature  core  by  means  of  a  screw  so  as  to  make  metallic  (elec- 


FIG.  24. 


Bosch  Low-tension  Alternating-current 
Armature  Mounted  on  Plain  Journal 
per  Revolution. 

1.  Field  magnets,  composite. 

2 .  Armature  plain  on  journal  bearings. 

3.  Insulated  bolt  to  which  one  end  of 

armature  winding  is  connected. 

4.  Terminal  with  binding  nut. 

5.  Metal  mounting  for  carbon  brush 

which  presses  against  end  of  3. 

6.  Front    bearing-plate     with    plain 

journal-bearing    and    felt    wick 
lubricator. 


Magneto   with    Rotary   Shuttle-wound 
Bearings.     Sectional  View.     Two  Sparks 

7.  Rear     bearing-plate     with     plain 

journal   bearing   and   felt   wick 
lubricator. 

8.  Felt  wick  with  coiled  spring  under  it. 

9.  Leather  washer. 

10.  Wick  holder. 

11.  Carbon  brush  with  coiled  spring. 
16.   Dust  cover  over  armature. 

20.    Steatite  insulating  washer  on  ter- 
minal 4. 


trie)  connection.  The  end  of  the  winding  is  metallically  con- 
nected to  the  insulated  bolt  3  which  passes  through  the  hollow 
rear  spindle  and  projects  beyond  the  end  of  the  spindle.  The 
black  around  the  bolt  3  indicates  insulating  material.  A  carbon 


32  ELECTRIC  IGNITION 

brush*  mounted  in  a  metallic  holder  5  is  pressed  against  the  end 
of  the  insulated  bolt  3  by  a  coiled  compression  spring.  The 
three  latter  parts  are  carried  in  an  insulated  terminal  4,  which  is 
provided  with  a  thumb-nut  for  holding  the  end  of  the  wire 
through  which  current  can  be  carried  to  other  apparatus.  A 
steatite  washer  20,  to  which  the  terminal  4  is  firmly  attached, 
holds  the  terminal  in  place  and  insulates  it. 

The  spindles  of  the  armature  are  of  the  plain  cylindrical 
journal  type  and  rotate  in  corresponding  bearings  in  the  plates 
6  and  7.  The  surface  of  each  journal  slides  over  the  surface  of 
its  supporting  bearing. 

The  carbon  brush  n  is  pressed  against  the  rear  head  of  the 
armature  by  a  coiled  compression  spring  so  as  to  make  electric 
connection  between  the  metal  of  the  armature  and  the  body  of 
the  magneto. 

The  path  of  the  current  that  is  generated  in  the  armature 
winding,  assuming  a  direction  of  flow,  is  from  the  insulated  end 
of  the  armature  winding  through  the  insulated  rod  3,  carbon 
brush  and  mounting  5,  terminal  4,  wire  leading  to  the  external 
apparatus  and  through  the  latter,  then  back  to  the  body  of  the 
magneto,  through  the  brush  1 1  to  the  armature  head,  from  which 
it  flows  to  and  through  the  core  to  the  end  of  the  winding  which 
is  connected  to  the  core.  The  current  also  passes  through  the 
armature  winding,  of  course. 

If  means,  such  as  brush  n,  were  not  provided  for  flow  of 

*  In  the  earlier  forms  of  electric  generators,  or  dynamo-electric  machines,  a 
"brush"  was  a  brushlike  bundle  of  copper  wires  used  to  make  sliding  contact 
between  electric  conductors  for  the  purpose  of  allowing  current  to  flow  from  one  to 
the  other.  By  common  usage  "brush"  has  come  to  mean  any  form  of  electric 
conductor  that  has  sliding  contact  with  another  part  for  the  purpose  just  stated. 
Ordinarily  the  brush  slides  continuously  over  the  part  against  which  it  bears. 
The  latter  may  be  either  all  electric  conductor,  or  it  may  be  part  conductor  and 
part  insulator.  In  some  cases  the  electric  contact  is  continuous;  in  others  it  is 
broken  by  insulation,  on  which  the  brush  rubs  part  of  the  time.  Either  the  brush 
or  the  part  on  which  it  rubs  may  be  stationary,  or  both  may  move  so  as  to  have 
motion  relative  to  each  other. 

A  carbon  brush  may  be  made  of  pulverized  charcoal  or  graphite  mixed  with 
suitable  binding  material  and  compressed  to  the  desired  shape.  Frequently  fine- 
woven  copper  or  brass  wire  (wire  gauze)  is  embedded  in  the  carbon  to  allow  the 
current  to  flow  more  freely  through  the  brush. 


ALTERNATING-CURRENT  MAGNETOS 


33 


current  between  the  armature  core  and  the  body  of  the  magneto, 
the  current  would  have  to  flow  through  the  journal  bearings. 
This  is  objectionable,  since  there  is  a  thin  film  of  oil  between  the 
rubbing  metal  surfaces  of  the  journal  and  its  bearing  when  they 
are  properly  lubricated  with  oil.  Oil  is  an  insulator,  and  there- 
fore prevents  to  some  extent  the  flow  of  current  even  when  the 
film  is  as  thin  as  in  bearings  of  this  sort.  The  electric  resistance 
of  the  oil  film  also  causes  heating  of  the  rubbing  surfaces  and 


FIG. 


Bosch  Low-tension  Alternating-current  Magneto  with 
Armature  Mounted  on  Ball  Bearings.  Sectional  View. 
lution. 

i.  Field  magnets,  composite.  21. 

2a.  Armature  on  ball  bearing. 

4.  Terminal  with  binding  nut.  22. 

5.  Metal  mounting  for  carbon  brush 

which  presses  against  end  of  21.        23. 
6a.  Front  end-plate  for  ball  race. 
ya.  Rear  end-plate  for  ball  race.  24. 

i6a.  Dust  cover  over  armature. 
20.  Steatite  insulating  washer  on  ter-       25. 

minal  4. 

tends  to  burn  the  oil,  thus  injuring  the  effectiveness  of  lubrica- 
tion.    All  of  this  is  objectionable. 

The  journal  bearings  are  each  lubricated  by  means  of  a  pencil- 
shaped  felt  wick,  one  of  which  is  shown  at  8.    It  is  pressed  up 


Rotary    Shuttle-wound 
Two  Sparks  per  Revo- 


Insulated  bolt  to  which  one  end  of 
armature  winding  is  connected. 

Inside  steatite  insulator  on  arma- 
ture. 

Outside  steatite  insulator  on  arma- 
ture. 

Carbon  brush  with  mounting  and 
coiled  spring. 

Screw  cover. 


34  ELECTRIC  IGNITION 

against  the  bottom  of  the  journal  by  a  coiled  spring.  The  felt 
wick  and  coiled  spring  are  held  in  place  by  a  wick-holder  10, 
which  is  a  hollow  screw.  A  leather  washer  9  is  placed  between 
the  screw  head  and  the  end-plate  into  which  the  wick -holder 
screws,  in  order  to  make  an  oil-tight  joint.  The  wick-holder 
has  a  small  hole,  or  holes,  through  its  sides  to  let  oil  in  to  the  wick 
from  the  oil  reservoir  which  surrounds  the  body  of  the  wick- 
holder.  One  of  these  small  holes  is  shown  in  the  wick-holder 
which  is  screwed  into  the  rear  bearing  plate  7. 

Fig.  25  shows  a  low-tension  magneto  with  ball  bearings  upon 
which  the  armature  rotates.  While  this  magneto  is  the  same  in 
its  general  nature  as  the  one  just  described,  it  differs  in  the  form 
and  location  of  some  of  its  parts.  There  are  no  oil  reservoirs 


FIG.  26.  FIG.  27. 

External  View  of  Magneto  shown          Splitdorf  Low-tension  Magneto.     Two 
Sectionally  in  Fig.  24.  Sparks  per  Revolution. 

and  no  wick-oilers,  since  the  ball  bearings  require  only  a  few 
drops  of  oil  once  a  month  or  so.  The  brush  24  for  making  elec- 
tric connection  between  the  armature  head  and  the  body  of  the 
magneto  is  at  the  head  end  of  the  armature  instead  of  at  the  rear 
end  as  in  the  other  machine,  and  is  perpendicular  to  the  spindles 
instead  of  parallel  to  them.  The  caption  immediately  beneath 
the  illustration  describes  the  parts  briefly. 

Fig.  26  is  a  full  view  of  the  magneto  shown  in  section  in  Fig.  24. 


ALTERNATING-CURRENT  MAGNETOS 


35 


The  driving  end  of  the  armature  spindle  is  shown  projecting 
forward  from  the  front  end  of  the  machine. 

Fig.  27  is  a  full  view  of  a  similar  magneto  showing  the  rear 
end  and  the  projecting  terminal  to  which  a  wire  leading  to  other 
apparatus  can  be  connected. 

Stationary  Shuttle-wound  Armature  Types. 

28.  Stationary  Armature  and  Rotary  Magnetic  Sleeve.  —  In- 
stead of  rotating  the  armature,  it  may  be  held  stationary  and 
the  required  magnetic  flux  through  the  core-neck  obtained  by 
rotating  an  inductor,  having  the  form  of  a  slotted  soft  steel 
sleeve,  between  the  armature  and  the  pole-pieces,  the  latter  being 
bored  considerably  larger  in  diameter  than  the  armature,  so  as  to 
leave  space  in  which  the  sleeve  can  rotate. 

Fig.  28  shows  a  magnetic  sleeve  for  rotating  between  a  sta- 
tionary armature  and  the  pole-pieces.  The  armature  is  shown 


82 


FIG.  28. 

Rotary  Magnetic  Sleeve  Inductor  for  a  Magneto  with  a  Stationary 
Armature  of  the  Shuttle  Type. 


FIG.  29. 

Stationary  Shuttle-wound  Armature  to  go  inside  of  the  Magnetic  Sleeve 
shown  in  Fig.  28. 

in  Fig.  29.  It  is  of  the  same  general  form  as  a  rotary  shuttle- 
wound  armature.  When  the  parts  are  assembled  the  armature 
lies  inside  the  sleeve. 

The  two  sides  of  the  magnetic  sleeve  have  the  form  of  pieces 


ELECTRIC   IGNITION 


cut  from  a  tube  by  slotting  it  lengthwise.     They  are  of  mild  steel 
as  already  stated,  and  are  held  together  by  disk-shaped  heads 


(G)  (H) 

FIG.  30. 

Magnetic  Flux  through  Stationary  Armature  Core  and  Rotary  Sleeve. 

of  non-magnetic  material,  such  as  brass,  bronze,  or  aluminum 
alloy,  attached  to  them  by  suitable  fastenings  (screws  in  this 
case).  One  of  the  heads  has  a  driving  spindle. 


ALTERNATING-CURRENT   MAGNETOS  37 

29.  The  action  of  the  magnetic  sleeve  in  causing  a  variation 
of  magnetic  flux  through  the  core-neck  of  the  armature  can  be 
understood  by  reference  to  Fig.  30,  in  which  the  sleeve  is  shown 
in  all  of  its  positions  for  maximum  magnetic  flux  and  for  no  flux 
through  the  core-neck,  no  allowance  being  made  for  armature 
lag.     The  direction  of  rotation  of  the  sleeve  is  indicated  by  the 
feathered  arrow,  which  may  be  taken  as  stamped  on  the  end  of 
the  sleeve.     The  general  direction  of  magnetic  flux  is  indicated 
by  the  lines  with  arrowheads  along  them. 

In  (A)  there  is  no  magnetic  flux  through  the  core-neck,  but 
a  slight  amount  occurs  through  the  crowned  sides  of  the  core. 
In  (B)  the  flux  has  a  maximum  value  through  the  core-neck  from 
top  to  bottom;  this  position  is  about  one-eighth  of  a  revolution 
later  than  (A).  In  (C)  the  sleeve  bridges  the  gap  between  the 
pole-pieces,  and  there  is  no  flux  through  the  core-neck.  In  (D) 
the  flux  again  has  a  maximum  value  through  the  core-neck,  from 
bottom  to  top,  which  is  in  the  opposite  direction  from  the  flux 
in  (B).  In  (E)  there  is  no  flux  through  the  core-neck.  This 
completes  the  first  half -re  volution,  starting  from  position  (A). 
It  may  be  noted  that  the  flux,  and  consequently  the  current, 
reaches  maximum  value  twice  during  half  a  revolution,  and  since 
the  flux  is  in  opposite  directions  in  (B)  and  (D),  the  current 
flows  in  opposite  directions  in  these  two  cases.  An  alternating 
current  is  therefore  generated. 

During  the  latter  half  of  the  revolution  the  variation  of  flux 
through  the  core-neck  is  the  same  as  that  during  the  first  half- 
revolution.  The  current  therefore  passes  through  two  complete 
cycles  during  one  revolution.  An  arc  can  be  drawn  four  times 
per  revolution  by  breaking  the  circuit  at  or  about  the  time  maxi- 
mum current  occurs. 

The  field-magnets  and  pole-pieces  for  a  magneto  with  a  sta- 
tionary shuttle-wound  armature  and  rotary  magnetic  sleeve  can 
be  of  the  same  form  as  those  for  a  rotary  shuttle  armature. 

30.  Note.  —  There  are  several  types  of  magnetos  designed 
especially  to  deliver  low-tension  alternating  current  for  use  in 
high-tension  ignition  systems.     The  more  important  of  these  will 
be  described  in  connection  with  high-tension  ignition. 


CHAPTER  III. 

DIRECT-CURRENT   MAGNETOS. 

31.  General.  —  By  the  use  of  a  suitable  form  of  armature 
between  the  pole-pieces  of  permanent  magnets,  a  direct  current 
can  be  obtained.  The  same  magnets  and  pole-pieces  can  be 
used  as  for  the  shuttle-wound  armature,  but  the  armature  core 


FIG.  31. 
Elementary  Form  of  Drum  Armature  between  Pole-Pieces  of  Magnets. 

is  different.  Several  forms  of  cores  are  used,  among  which  one 
in  the  form  of  a  cylinder,  and  another  having  the  form  of  a  ring, 
are  most  common.  The  cylinder  generally  has  lengthwise  slots 
to  receive  the  winding.  An  armature  with  a  cylindrical  core  is 

38 


DIRECT-CURRENT  MAGNETOS  39 

generally  known  as  a  drum  armature.  This  applies  whether 
the  core  has  a  smooth  cylindrical  surface  or  is  slotted  as  just 
stated. 

32.  Elementary  Form  of  Drum  Armature.  —  A  cylindrical  core 
A  with  one  turn  of  insulated  wire  W  around  it  is  shown  in  Fig.  31 
in  the  magnetic  field  between  the  pole-pieces  of  a  set  of  permanent 
magnets.     The  wire  is  continuous  (without  ends).     The  mag- 
netic flux  is  from  the  N  pole  across  the  air-gap  between  the  N 
pole  and  the  core  to  the  core,  through  the  core  and  across  the 
air-gap  between  the  core  and  the  S  pole  to  the  latter.     The  same 
number  of  lines  of  magnetic  force  pass  through  the  smooth  cylin- 
drical core  whatever  its  position  with  regard  to  rotation  about 
its  axis.     This  is  also  approximately  true  of  a  slotted  cylindrical 
core  of  the  usual  form. 

33.  Generation  of  Current.  —  When  this  elementary  armature 
is  standing  in  the  position  shown  in  Fig.  31,  all  of  the  magnetic 
lines  of  force  in  the  core  pass  through  the  space  inclosed  by  the 
wire.     Other  positions  of  the  armature  are  shown  in  Fig.  32. 
When  in  position  (A)  part  of  the  magnetic  flux  through  the  core 
passes  through  the  space  inclosed  by  the  loop  of  wire,  and  part 
passes  outside  of  the  loop.     In  (B)  none  of  the  flux  is  through 
the  space  inclosed  by  the  loop.      In  (C)  part  of  the  flux  in  the 
core  is  through  the  coil  space,  and  in  (D),  half  a  revolution  from 
the  position  in  Fig.  31,  all  of  the  flux  through  the  core  passes 
through  the  coil.     The  direction  of  the  flux  through  the  coil 
space  is  in  the  opposite  direction  in  (D)t  relative  to  the  coil, 
from  its  direction  in  Fig.  31,  where  it  enters  the  coil  space  from 
the  side  next  to  the  feathered  arrow  cut  into  the  core.     In  (D) 
the  flux  enters  the  coil  space  from  the  side  opposite  the  feathered 
arrow,  which  rotates  with  the  core  and  coil. 

When  the  armature  is  rotating,  the  positions  at  which  all  of 
the  flux  in  the  core  passes  through  the  coil,  and  those  at  which 
none  of  the  flux- passes  through  the  coil,  occur  later  in  the  revo- 
lution on  account  of  magnetic  lag  and  the  reactions  which  occur 
on  account  of  the  electric  current  generated  in  the  coil  and  other 
parts. 

For  convenience  in  discussing  the  manner  in  which  a  direct 


ELECTRIC  IGNITION 


FIG.  32. 
Current  Flow  in  Winding  of  Elementary  Drum  Armature. 

current  is  obtained,  the  effect  of  magnetic  lag  and  armature 
reactions  will  be  neglected.* 

As  the  armature  passes  through  the  position  shown  in  Fig.  32 
at  (X)  while  rotating  in  the  direction  indicated  by  the  feathered 
arrow,  electromotive  force  is  generated  in  the  wire  of  the  coil 
and  current  flows  through  the  wire  in  the  direction  indicated  by 

*  It  is  not  thought  necessary  to  discuss  more  fully  the  effect  of  cross-magnet- 
ization and  armature  reactions. 


DIRECT-CURRENT  MAGNETOS  41 

the  arrow  on  the  wire.  The  direction  of  current  flow  is  similarly 
indicated  in  (£),  (C),  (£),  and  (F).  There  is  no  current  flow 
in  position  (D)  and  in  the  position  shown  in  Fig.  31.  The  elec- 
tromotive force  at  any  instant  is  proportional  to  the  rate  at 
which  the  stretches  of  wire  along  the  cylindrical  surface  of  the 
core  are  cutting  through  the  lines  of  force.  This  rate  corre- 
sponds to  the  rate  of  change  in  the  amount  of  magnetic  flux 
through  the  space  inclosed  by  the  coil.  The  current  is  approxi- 
mately proportional  to  the  electromotive  force  at  any  instant. 
In  the  positions  shown  in  Fig.  31,  and  at  (D)  in  Fig.  32,  the  wire 
is  not  cutting  through  lines  of  magnetic  force,  hence  there  is 
neither  electromotive  force  nor  current. 

In  (E)  and  (F)  the  direction  of  current  flow  through  the  wire 
is  opposite  that  in  (A),  (B),  and  (C).  In  (E)  and  (F)  the  arrow 
indicating  the  direction  of  flow  through  the  stretch  of  wire 
across  the  front  end  of  the  core  points  in  the  same  direction  as 
the  feathered  arrow  engraved  in  the  end  of  the  core,  while  in 
positions  (A),  (B),  and  (C)  the  arrows  point  in  opposite  direc- 
tions. The  reason  why  the  current  changes  its  direction  of  flow 
has  been  discussed  in  §  22.  It  should  be  noted  that  the  direction 
of  current  flow  through  the  portion  of  the  wire  that  lies  across 
the  end  of  the  armature  core  is  always  from  the  S  pole  toward 
the  N  pole  when  the  armature  is  rotating  clockwise.  In  other 
words,  the  current  flow  through  the  wire  next  to  the  south  pole 
is  always  toward  the  observer  when  the  rotation  is  clockwise.* 

34.  Commutation  of  Current  in  a  Direct-current  Generator.  — 
In  Fig.  33  the  coil  of  wire  is  cut  in  two  at  the  front  end  and  the 
ends  fastened  to  two  parts,  i  and  2,  which  are  approximately 
half-rings  of  metal.  Brushes,  3  and  4,  of  metal,  carbon,  or  some 
other  conductor  of  electricity,  bear  on  the  rings  at  points  (really 
areas)  diametrically  opposite  each  other.  From  these  brushes 
wires  connect  to  an  external  circuit  5.  While  the  armature  is 
rotating  clockwise  through  the  position  shown,  the  current  flows 
from  brush  3  (next  to  the  S  pole)  to  the  external  circuit  5,  through 
the  external  circuit  and  then  to  the  brush  4.  This  continues  as 

*  If  the  rotation  were  in  the  opposite  direction,  the  current  flow  would  also 
always  be  in  the  opposite  direction  from  that  indicated. 


ELECTRIC  IGNITION 


long  as  brush  3  is  in  contact  with  segment  i  and  while  current  is 
generated  in  the  armature  coil.  When  the  armature  reaches  a 
position  similar  to  that  in  Fig.  31,  which  may  be  called  the 
"  dead  "  position  of  the  coil,  the  open  spaces  between  the  two 
segments  have  come  under  the  brushes.  The  brushes  therefore 
change  from  one  segment  to  the  other  of  the  ring  while  no  current 
is  flowing,  and  consequently  there  is  no  spark  formed  during  this 


VWWIAAJ 
FIG.  33. 
Two-segment  Commutator  and  Brushes  of  Elementary  Drum  Armature. 

change  from  one  segment  to  the  other.  When  segment  2  is  alone 
in  contact  with  brush  3  and  current  is  again  generated,  the  flow 
is,  as  before,  from  brush  3  through  the  external  circuit  5  to  brush  4. 
By  the  use  of  this  two-segment  commutator  the  flow  of  current 
through  the  external  circuit  is  caused  to  be  always  in  the  same 
direction.  The  flow  of  current  in  the  armature  wire  alternates 
as  before,  however. 

Since  the  flow  of  current  is  always  from  brush  3  to  the  external 
circuit,  this  brush  is  called  the  positive  brush  and  is  usually  indi- 
cated by  the  sign  +.  The  other  brush,  4,  toward  which  the 
current  flows,  is  indicated  by  the  sign  — ,  and  is  called  the 
negative  brush. 


DIRECT-CURRENT  MAGNETOS  43 

A  current  which  flows  in  one  direction  only  is  called  a  direct 
current.  As  produced  by  the  elementary  generator  shown  in 
Fig.  33,  it  is  intermittent,  or,  more  specifically,  pulsating. 

35.  Continuous-current  Electric  Generator.  —  In  order  to  ob- 
tain a  continuous  current  it  is  necessary  to  use  more  than  one 
armature  coil  and  more  than  two  commutator  segments.  To 
operate  successfully  for  the  usual  requirements,  the  coils  are 
spaced  uniformly  around  the  core,  and  the  commutator  segments 
are  all  of  the  same  width  circumferentially.  In  the  more  usual 
constructions  there  is  the  same  number  of  commutator  segments 
as  there  are  coils,  but  not  infrequently  twice  as  many  commutator 
segments  as  coils  are  used.  Each  coil  may  have  only  one  turn, 
as  in  Fig.  33,  or  each  may  have  several  turns,  or  wraps.  It  is 
probably  that  in  all  direct-current  generators  intended  for  igni- 
tion purposes,  each  armature  coil  has  several  turns. 


FIG.  34. 
Thin  Disk  of  a  Laminated  and  Slotted  Drum  Armature. 

36.  Laminated  Drum  Armature  Core.  —  In  the  better  genera- 
tors for  direct  current  the  armature  core  is  built  up  of  a  number 
of  thin  disks  cut  from  sheet  metal  and  placed  side  by  side  in  the 
same  manner  as  has  been  described  for  shuttle-wound  armatures 
and  for  the  same  reason.  One  of  the  disks  for  a  direct-current 
generator  is  shown  in  Fig.  34.  The  metal  is  cut  out  at  regular 


44 


ELECTRIC   IGNITION 


intervals  around  the  periphery  to  leave  openings  which,  when 
the  disks  are  grouped  together  in  the  armature,  form  the  slots 
in  which  the  wire  is  wound.  The  central  opening  is  for  the 
armature  spindle,  which  is  usually  all  in  one  piece  and  passes 
through  the  core.  It  is  good  practice  to  place  a  brass  sleeve,  or 
quill,  between  the  steel  spindle  and  the  core-disks. 

37.   A  complete  drum  armature  for  direct  current  is  shown  in 
Fig.  35.     This  armature  has  12  coils,  each  of  several  turns  of 


FIG.  35. 
Drum  Armature  of  Direct-current  Electric  Generator. 

wire  wound  in  the  slots  of  the  core,  and  12  segments  in  the 
commutator. 

38.   A  commutator  similar  in  general  form  to  that  on  the  arma- 
ture in  the  preceding  figure  is  shown  in  Fig.  36,  in  which  (A)  is  a 


/-x .. .. 


(A)  (B) 

FIG.  36. 
Commutator  for  Direct-current  Electric  Generator.     Twelve  Segments. 

view  of  the  complete  commutator,  and  (B)  is  a  longitudinal  sec- 
tion.    The  segments  are  dove-tailed  and  held  in  place  by  the 


DIRECT-CURRENT  MAGNETOS  45 

correspondingly  dove-tailed  inner  sleeve  and  ring.  Insulation  i 
is  placed  between  the  adjacent  copper  segments,  and  at  2,  3,  4, 
and  5  between  the  segments  and  the  metal  sleeve.  The  annular 
space  6  may  or  may  not  have  insulation  in  it,  according  to  the 
will  of  the  designer.  There  is  a  possibility  of  moisture  collecting 
in  this  space  if  it  is  not  filled  with  insulation.  The  insulation 
between  adjacent  segments  must  be  of  some  material  that  will 
withstand  heat  and  is  not  readily  burned  by  the  sparks  that 
form  as  the  brushes  pass  from  one  segment  to  the  next,  especially 
when  the  brushes  are  not  properly  set.  Mica  or  some  composi- 
tion composed  chiefly  of  mica  is  used  for  this  insulation. 

Various  methods  of  fastening  the  ends  of  the  armature  coils 
to  the  segments  are  used.  A  common  one  is  to  notch  or  slit  the 
end  of  the  segment  and  solder  the  wire  into  the  notch.  A  hard 
solder  (one  that  does  not  melt  at  a  low  temperature)  should  be 
used,  so  that  it  will  not  melt  and  fly  out  in  case  the  commutator 
becomes  hot.  It  is  well  to  swedge  the  segment  down  on  the 
wire  to  prevent  the  latter  from  flying  out  in  case  the  solder  melts. 
Screws  are  sometimes  used  to  fasten  the  wire  to  the  segments, 
but  they  are  apt  to  become  loose,  unless  soldered,  on  account  of 
the  expansion  and  contraction  due  to  heating  while  in  service 
and  cooling  while  at  rest. 

39.  Armature  Connections.  —  Fig.  37  is  a  diagram  showing 
conventionally  how  the  ends  of  the  armature  coils  are  brought  to 
the  segments  of  the  commutator.  This  diagram  is  for  an  arma- 
ture with  12  coils  and  the  same  number  of  commutator  segments, 
intended  for  use  in  a  bipolar  generator.  Only  one  turn  of  wire 
for  each  coil  is  represented,  but  each  coil  may  have  several  turns. 

Starting  at  segment  i,  connection  is  made  to  one  side  A  of  a 
coil  lying  in  a  slot  of  the  core.  Side  A  is  connected,  across  the 
back  end  of  the  core,  to  the  side  A'  of  the  same  coil,  and  A'  is 
connected  to  the  segment  2.  Segment  2  is  also  connected  to  B, 
which  is  connected  across  the  back  end  of  the  core  to  B',  and  the 
latter  is  connected  to  segment  3.  The  same  method  of  connec- 
tion is  followed  out  for  all  of  the  coils,  thus:  3,  C,  C',  4;  4,  D,  D', 
5;  and  so  on  to  12,  L,  L',  i. 

The  coils  are  not  shown  connected  in  the  successive  order  in 


46  ELECTRIC  IGNITION 

which  they  have  to  be  wound  on  the  core.  The  successive  order 
of  winding  is  A,  H,  C,  J,  E,  L,  G,  B,  7,  D,  K,  F.  If  the  coils 
were  connected  to  the  commutator  in  the  order  of  their  winding, 
as  just  given,  the  lengths  of  the  different  circuits  through  the 


FIG.  37. 

Winding  Diagram  of  Direct-current  Armature  with  Twelve  Coils  and  Twelve 
Commutator  Segments. 

armature  would  not  be  uniform,  and  the  armature  would  not 
operate  as  satisfactorily  as  when  the  connections  are  made  as  has 
been  shown. 

The  direction  of  current  flow  through  the  connections  to  the 
commutator  is  indicated  by  the  arrowheads  on  the  lines  repre- 
senting the  connections. 

The  brushes  are  shown  in  contact  with  the  commutator,  and 
are  indicated  as  positive  and  negative  by  the  signs  +  and  — . 
It  can  be  seen  that  the  -f  brush  electrically  connects  the  seg- 
ments i  and  2,  to  which  the  ends  of  the  coil  A  are  attached,  when 


DIRECT-CURRENT  MAGNETOS 


47 


the  armature  is  in  the  position  of  its  rotation  shown  in  the  dia- 
gram. The  brush  bridges  the  insulation  between  i  and  2.  This 
corresponds  to  the  connection  that  occurs  between  the  two  half- 


Direct-current  Magneto. 

1.  Field  magnets. 

2.  Pole-pieces. 

3.  Armature. 

4.  Brass  tube  enclosing  armature. 

5.  Commutator. 

6.  Brush  that  bears  on  commutator. 

7.  Brush-holder.     Insulated. 

8.  Insulation    between    brush-holder 

and  tube  4. 

9.  Insulation  around  screw  that  holds 

brush-holder  in  place. 
10.    Coil-spring   for  pressing   brush   6 
against  commutator. 


FIG.  38. 
Hercules  Electric  Co.,  Indianapolis,  Ind. 


11.  Terminal  for  external  wire. 

12.  Bearing  for  armature  spindle. 

13.  Bell-shaped  friction  pulley. 

14.  Friction  facing  of  pulley  13. 

1 5 .  Collar  for  speed  governor. 

16.  Governor  balls  and  arms. 

17.  Governor  spring. 

18.  Setscrew. 

19.  Base  of  magneto. 

20.  Clamps  for  holding  magnets  against 

pole-pieces. 

21.  Clamp  bolt. 

22.  Name  plate. 


rings  in  Fig.  33  when  the  armature  in  the  latter  figure  has  rotated 
one-quarter  revolution  from  the  position  shown.  But  in  Fig.  3  7 
the  coil  A  is  in  its  dead  position  when  thus  short-circuited  by 


48  ELECTRIC  IGNITION 

the  brush,  just  as  the  coil  is  in  Fig.  33  when  the  ends  of  the  half- 
rings  are  under  the  brushes,  therefore  no  electromotive  force  is 
induced  in  the  coil  to  cause  current  flow  in  that  coil  which  would 
cause  sparking  at  the  brush  when  segment  2  passes  from  contact 
with  the  brush  and  thus  breaks  the  short-circuit  of  coil  A .  The 
same  applies  to  coil  G,  which  is  shown  short-circuited  by  the 
negative  (— )  brush.  It  also  applies  to  all  the  other  coils  as 
their  segments  pass  successively  under  the  brushes. 

40.  A  complete  direct-current  magneto  for  giving  a  continuous 
current  is  shown  in  Fig.  38.  The  armature  is  surrounded  by  a 
brass  tube  4  through  which  the  pole-pieces  project  so  as  to  come 


FIG.  39. 
Photographic  View  of  Direct-current  Magneto  shown  in  Fig.  38. 

close  to  the  armature.  This  tube,  together  with  the  heads  which 
carry  the  spindle  bearings,  form  a  dust-  and  water-proof  protec- 
tion for  the  armature.  The  brushes  are  made  of  phosphor-bronze 
wire  gauze  pressed  in  dies  to  a  suitable  form  around  a  carbon 
core.  The  carbon  acts  as  a  lubricator  for  the  rubbing  surfaces 
of  the  brushes  and  commutator.  A  bell-shaped  friction  pulley 
13  is  carried  on  the  driving  end  of  the  armature  spindle.  This 
pulley  is  faced  with  a  suitable  friction  material,  such  as  leather, 
paper  composition,  or  rawhide,  which  is  pressed  by  spring  action 
axially  against  a  rotating  part,  such  as  a  flywheel  or  pulley  that 
drives  the  friction  pulley.  The  speed  of  rotation  of  the  armature 
is  controlled  by  a  shaft  governor  of  the  fly-ball  type.  The  balls 


DIRECT-CURRENT   MAGNETOS 


49 


are  drawn  toward  each  other  radially  by  a  pair  of  coiled  tension 
springs,  one  of  which,  17,  is  shown.  As  the  speed  increases  the 
balls  move  out  radially  and  reduce  the  pressure  between  the 


FIG.  40. 

Direct-current  Magneto  with  Friction  Pulley  and  Speed  Governor.     Tritt  Elec- 
tric Company,  Union  City,  Indiana. 

facing  of  the  friction  pulley  and  the  flywheel.  This  action  allows 
the  friction  pulley  to  slip  enough  on  the  flywheel  to  keep  the 
speed  of  the  armature  down  to  the  required  rate. 

Fig.  39  is  a  photographic  view  of  a  direct-current  magneto  of 
the  general  type  shown  in  the  preceding  figure.  Fig.  40  illus- 
trates another  machine  that  operates  in  a  similar  manner. 


CHAPTER  IV. 
TESTING  FOR  DIRECTION   OF  CURRENT. 

Chemical  Tests. 

41.   Water  Test.     Bubbles  Form  at  Submerged  Wire-End.  - 

To  about  half  a  pint  of  water  in  a  glass  tumbler  or  other  vessel 
that  is  not  a  conductor  of  electricity  add  any  one  of  the  following : 

Common  salt  (NaCl),  one  teaspoonful; 

Common  washing  soda  (sal  soda,  Na2CO3),  one  teaspoonful; 

Sulphuric  acid  (H2SO4),  half  teaspoonful  of  the  strength  sold 
at  drug  stores; 

Hydrochloric  acid  (HC1),  half  teaspoonful  of  the  strength  sold 
at  drug  stores. 

Connect  a  small  wire  with  each  of  the  two  brushes  of  a  direct- 
current  generator,  or  with  the  positive  and  negative  terminals  of 
any  source  of  direct-current  supply,  and  dip  the  free  bare-metal 
ends  of  the  wires  into  the  impure  water,  first  keeping  the  ends 
as  far  apart  as  possible  and  then  gradually  bringing  them  toward 
each  other,  without  allowing  them  to  touch. 

Bubbles  of  gas  will  form  on  and  rise  from  the  submerged  end 
of  the  wire  that  is  connected  to  the  negative  (— )  side  of  the 
source  of  direct-current  supply.  (This  test  does  not  apply  to 
alternating  current.)  With  the  small  currents  and  pressures 
commonly  used  for  ignition  purposes,  there  is  no  appreciable 
formation  of  bubbles  at  the  positive  wire-end. 

There  are  numerous  other  substances  that  can  be  used  for 
adding  to  the  water  to  make  it  impure  for  the  direction-of -current 
test.  In  fact,  water  from  city  mains  often  contains  enough 
matter  in  solution  to  make  it  impure  enough  (chemically  speak- 
ing) for  this  test. 

The  passage  of  the  direct  current  through  the  impure  water 
decomposes  it  into  its  chemical  elements,  hydrogen  and  oxygen, 
each  of  which  is  a  gas.  This  action  is  more  or  less  indirect  so 

50 


TESTING  FOR  DIRECTION  OF  CURRENT  $1 

far  as  the  water  itself  is  concerned.  The  hydrogen  is  liberated 
at  the  negative  terminal.  When  water  is  decomposed  it  gives 
two  volumes  of  hydrogen  for  each  volume  of  oxygen.  The 
oxygen  tends  to  collect  at  the  positive  terminal,  but  at  least 
part  of  it  is  absorbed  by  the  water  and  thus  disappears  so  far  as 
its  being  a  gas  is  concerned. 

Each  of  the  submerged  ends  of  the  wire  is  called  an  electrode. 
The  liquid,  in  this  case  impure  water,  is  called  the  electrolyte. 
The  positive  electrode  (the  one  connected  to  the  positive  side  of 
current  supply)  is  called  the  anode,  and  the  negative  electrode 
is  called  the  cathode. 

The  decomposition  of  the  water  sets  up  a  counter-electromotive 
force  of  about  1.48  volts.  This  is  about  the  maximum  electro- 
motive force  of  one  cell  of  ordinary  dry  electric  batteries  such 
as  are  in  common  use  for  ignition.  One  cell  of  such  a  battery 
will  not  therefore  generally  give  bubbles  at  the  electrode  in  this 
test.  At  least  two  cells  must  be  connected  in  series  to  make 
certain  of  producing  bubbles.  Different  methods  of  connecting 
cells  to  form  a  battery  are  given  later. 

42.  Color  Test.  —  If  a  tablespoonful  of  sal  ammoniac  (ammo- 
nium chloride,  NH4C1)  is  dissolved  in  half  a  pint  of  water,  and 
the  bare  ends  of  two  wires  placed  in  the  liquid  as  described  in 
the  preceding  article,  the  liquid  around  the  positive  terminal, 
or  anode,  will  turn  blue,  and  bubbles  will  form  at  the  negative 
terminal,  when  current  flows. 

There  are  several  substances  that  will  give  color  tests  of  this 
nature.  Different  colors  are  obtained  according  to  the  sub- 
stances used. 

Convenient  devices  for  making  color  tests  are  found  on  the 
market.  A  small  glass  tube  some  two  inches  in  length,  set  in  a 
mounting  and  having  suitable  terminals,  is  a  convenient  form. 
The  instrument  should  be  marked  so  that  there  can  be  no  mistake 
in  determining  which  of  the  two  wires  connected  to  it  to  test 
them  is  positive  or  negative. 


ELECTRIC  IGNITION 


Test  with  Magnetic  Needle. 

43.  Magnetic-compass  Test.  —  Place  the  wire  which  carries 
the  current  immediately  above  the  case  in  which  the  magnetic 
needle  is  mounted,  as  in  Fig.  41,  so  that  the  direction  of  the  wire 
is  the  same  in  general  as  the  length  of  the  magnetic  needle.  If 
the  wire  is  not  insulated  it  is  best  not  to  let  it  touch  the  metal 
of  the  case.  It  is  immaterial  whether  it  touches  the  glass.  The 


Positive 


—  Negative 


—  Negative 
(A) 


FIG.  41. 


Magnetic  Compass  Indicating  Direction  of  Flow  of  Electric  Current  by  the 
Deflection  of  the  Needle. 

needle  will  be  deflected  from  its  north-and-south  position  during 
the  time  a  direct  current  flows  through  the  wire  placed  in  this 
position. 

If  the  current  flows  from  the  north  toward  the  south  above 
the  needle,  it  will  be  deflected  in  a  clockwise  direction  as  indicated 
at  (A).  In  other  words,  the  needle  will  be  turned  through  part 
of  a  revolution  in  the  same  direction  that  the  hands  of  a  clock 
rotate. 

A  current  from  the  north  above  the  needle  turns  it  clockwise  is  a 
convenient  expression  by  which  to  remember  the  action  of  a 
direct  current  on  a  magnetic  needle. 


TESTING  FOR  DIRECTION  OF  CURRENT  53 

If  the  current  flows  in  the  opposite  direction  (toward  the 
north)  above  the  needle,  it  will  be  rotated  in  the  opposite  direc- 
tion as  shown  in  (B).  By  placing  the  wire  beneath  the  needle, 
the  action  on  the  needle  will  be  the  reverse  of  that  when  the  wire 
is  above  the  needle. 

44.  Extemporized  Compass  Needle.  —  An  ordinary  sewing 
needle  magnetized  and  floated  on  water  in  a  non-magnetic  vessel 
can  be  conveniently  used  in  the  absence  of  a  compass.     The 
needle  can  be  magnetized  by  bringing  it  in  contact  with  a  magnet, 
or  by  means  of  an  electric  current.     The  latter  method  is  ex- 
plained in  Chapter  VI. 

If  the  sewing  needle  is  highly  polished,  as  when  new,  it  can 
be  floated  on  water  by  first  drying  it  and  then  rubbing  it  with 
a  slightly  oily  cloth  or  one's  fingers,  slightly  oily.  If  then  laid, 
or  dropped  lightly,  on  the  water  it  will  float  and  quickly  assume 
a  north-and-south  direction.  A  needle  that  is  bright  and  prop- 
erly oiled  will  float  a  day  or  more.  The  action  of  the  electric 
current  upon  this  floating  needle  is  the  same  as  on  the  pivotally 
supported  needle  in  a  compass. 

Another  method  of  floating  the  needle  is  to  lay  it  on,  or  stick 
it  through,  a  flat  piece  of  cork  or  paraffin. 

A  cup  or  saucer  is  convenient  for  holding  the  water.  A  brass, 
copper,  or  aluminum  vessel  will  answer,  but  the  wire,  if  bare  of 
insulation,  should  not  be  allowed  to  touch  the  vessel  in  two 
places  at  the  same  time.  A  steel  or  iron  vessel  is  not  so  satis- 
factory on  account  of  the  tendency  of  the  needle  to  float  up 
against  the  side. 

45.  Test  with  Measuring  Instruments.  —  Many  of  the  amme- 
ters and  voltmeters  for  measuring  current  and  pressure  are  made 
so  that  the  direction  of  the  current  flowing  through  them  can 
be  told.     The  terminals  of  the  instrument  are  marked  +  and  — , 
or  P-\-  and    N  — .    The  indicating  needle,  or  pointer,  of  the 
instrument  moves  so  as  to  give  a  reading  on  the  graduated  scale 
only  when  the  wires  are  connected  to  the  instrument  terminals 
in  accordance  with  the  signs;  the  positive  wire  to  the  terminal 
with  the  +  sign,  and  the  negative  wire  to  the  terminal  with 
the  —  sign. 


CHAPTER  V. 


ELECTRIC   MEASURING  INSTRUMENTS.* 

46.  General.  —  It  is  often  desirable  to  test  a  battery  to  deter- 
mine its  condition  by  measuring  its  voltage  and  the  amount  of 
current  that  it  will  give;  also  to  measure  the  amount  of  current 
that  an  ignition  system  is  using.  For  this  purpose  numerous 
types  of  small  portable  instruments  have  been  developed,  and  a 
lesser  number  of  instruments  intended  to  be  fixed  in  place.  The 
smaller  portable  instruments  frequently  resemble  a  watch  or 
pocket  compass  in  general  appearance,  and  are  about  the  size 
of  a  large  watch.  These  instruments  ordinarily  operate  on  the 
principle  that  an  electric  current  flowing  through  a  coil  of  wire 
attracts  or  repels  a  permanent  magnet  or  a  piece  of  magnetic 
material  and  causes  it  to  move  when  it  is  mounted  so  as  to  allow 

movement,  or  upon  the  principle  that 
two  coils  of  wire  with  current  flowing 
through  them  attract  or  repel  each  other 
so  that  one  coil  is  moved  when  mounted 
for  such  movement. 

The  chief  difference  between  the  am- 
meter, for  measuring  current,  and  the 
voltmeter,  for  measuring  pressure,  is 
that  the  ammeter  has  a  coil,  or  coils, 
of  comparatively  thick  wire  of  short 
length  which  has  a  very  low  resistance, 
and  the  voltmeter  has  a  coil,  or  coils, 
Portable  Ammeter  for  Measur-  of  very  thin  wire  of  great  length  and 

ing  Electric  Current.    Small    verv  frjgh  resistance. 

47.   Ammeters.— A  small   portable 
ammeter  for  measuring  current  up  to  30  amperes  is  illustrated  in 

*  This  chapter  is  intended  to  deal  with  only  such  measuring  instruments  as 
are  used  in  connection  with  ignition  systems,  and  only  to  an  extent  sufficient  to 
give  a  general  idea  of  their  nature  and  use.  It  is  not  thought  desirable  to  go  into 
details  of  measuring  instruments  in  a  work  of  this  nature. 

54 


FIG.  42. 


ELECTRIC   MEASURING  INSTRUMENTS 


55 


Fig.  42.  The  indicating  needle  (pointer,  hand)  which  indicates 
the  amount  of  current  flowing  through  the  ammeter  is  pivoted 
at  the  center  of  the  instrument  and  shown  pointing  to  zero  of 
the  graduated  scale.  When  current  is  flowing  through  the  in- 
strument, the  needle  is  deflected  and  points  to  the  reading  that 


FIG.  43. 

Stationary  Ammeter.     Weston  Electrical  Instrument  Company,  Newark, 

New  Jersey. 

corresponds  to  the  number  of  amperes  of  current  flowing.  One 
of  the  terminals  is  the  projection  at  the  bottom  of  the  case,  and 
the  other  is  at  the  free  end  of  the  attached  wire. 

When  testing  a  primary  battery,  one  terminal  of  the  ammeter 
is  electrically  connected  to  one  terminal  of  the  battery,  and  the 


56  ELECTRIC  IGNITION 

other  terminal  of  the  ammeter  is  electrically  connected  to  the 
other  terminal  of  the  battery.  Current  from  the  battery  then 
flows  through  the  ammeter.  (The  ammeter  should  not  be  used 
in  this  manner  for  testing  a  storage  battery,  unless  the  instru- 
ment is  especially  designed  for  such  use,  and  current  should  not 
be  allowed  to  flow  longer  than  necessary  to  obtain  a  reading  — 
not  longer  than  two  or  three  seconds.) 

TO  measure  the  current  flowing  through  any  circuit,  the  am- 
meter must  be  interposed  in  the  circuit  (cut  into  the  circuit)  so 
that  all  of  the  current  of  the  circuit  will  flow  through  the  am- 
meter. Thus,  the  ammeter  may  be  cut  into  a  circuit  that  has 
a  wire  held  by  a  binding  screw,  by  disconnecting  the  wire  from 
the  binding  screw  and  connecting  one  terminal  of  the  ammeter 

to  the  binding  screw,  then  connecting 
the  other  terminal  of  the  ammeter  to  the 
disconnected  end  of  the  wire. 

Fig.  43  is  a  high-grade  ammeter  in- 
tended to  be  used  in  a  fixed  position,  as 
on  a  switchboard.  Its  range  of  current 
is  from  zero  to  50  amperes.  Similar 
instruments  are  made  with  ranges  re- 
spectively up  to  i,  5,  10,  15,  25,  and  75 
amperes. 

48.  Voltmeters.  —  Fig.  44  is  a  small 
TIG.  44.  portable  voltmeter  reading  up    to  10 

Portable  Voltmeter  for  Measur-  volts.     It  resembles,  in  general  appear- 


ing Electric  Pressure.  Small  ance?  ^  sman  ammeter  just  described. 
One  terminal  is  at  the  bottom  of  the 
case,  and  the  other  at  the  free  end  of  the  attached  wire. 

For  measuring  voltage,  the  terminals  of  the  voltmeter  are 
electrically  connected  to  the  two  points  between  which  the 
pressure  is  to  be  measured,  one  terminal  of  the  voltmeter  to 
each  point.  It  is  immaterial  whether  the  circuit  is  otherwise 
open  or  closed  between  the  points  of  connection,  so  far  as  the 
action  of  the  voltmeter  is  concerned.  Thus,  the  voltage  of  a 
battery  can  be  measured  by  connecting  the  terminals  of  the 
voltmeter  to  the  terminals  of  the  battery,  either  while  the  battery 


ELECTRIC   MEASURING  INSTRUMENTS  57 

has  no  other  connection  to  it  (on  open  circuit),  or  while  the 
battery  is  connected  in  circuit  and  delivering  current  for  its 
regular  service.  The  reading  of  the  voltmeter  will  not  generally 
be  the  same  under  the  two  conditions,  but  this  is  because  the 
difference  of  pressure  between  the  battery  terminals  is  not  the 
same  while  it  is  delivering  current  as  when  it  is  on  open  circuit. 

The  amount  of  current  that  flows  through  the  voltmeter  while 
measuring  pressure  is  so  small  as  to  have  no  appreciable  effect 
on  the  action  of  the  battery  or  the  circuit  to  which  the  voltmeter 
is  connected. 

49.  Volt-ammeters.  —  It  is  quite  usual  to  combine  a  volt- 
meter and  an  ammeter  in  one  instrument,  called  a  volt-ammeter. 
In  some  of  these  only  one  indicating  needle  (hand,  pointer)  is 
used,  and  the  reading  scale  has  two  graduations,  one  for  amperes 
and  the  other  for  volts.  Such  an  instrument  cannot  be  used 
for  measuring  both  current  and  pressure  at  the  same  instant. 
Other  volt-ammeters  are  made  up  of  two  complete  instruments, 
a  voltmeter  and  an  ammeter,  and  can  be  used  for  measuring 
both  current  and  pressure  at  the  same  time. 

Fig.  45  is  a  small  portable  volt-ammeter  of  the  type  having 
only  one  indicating  needle.  The  reading  scale  is  graduated  to 
'10  volts  and  30  amperes.  The  instrument  has  three  terminals. 
The  one  at  the  top  is  for  both  volts  and  amperes.  The  left- 
hand  one  at  the  bottom  is  for  volts,  and  the  other  for  amperes. 
For  measuring  purposes,  the  top  terminal  and  the  left-hand  one 
at  the  bottom  are  connected  respective  to  the  points  between 
which  the  pressure  is  to  be  measured.  For  measuring  current, 
the  connections  are  made  to  the  top  terminal  and  the  right-hand 
lower  terminal. 

A  comparatively  small  volt-ammeter  for  use  in  connection 
with  storage  batteries  (see  Fig.  102)  is  shown  in  Fig.  46.  Only 
one  indicator  needle  is  used.  The  needle  is  shown  in  its  zero 
position,  which  is  not  at  the  end  of  the  graduated  scale.  The 
lower  scale  is  for  amperes,  and  is  graduated  in  both  directions 
from  its  zero.  When  the  instrument  is  used  as  an  ammeter, 
the  needle  is  deflected  either  to  the  right  or  the  left,  according 
to  the  direction  in  which  the  current  is  flowing  through  the 


ELECTRIC  IGNITION 


instrument.     To  obtain  a  voltage  reading,  the  push-button  V 
below  the  scale  is  pressed  in  and  held  while  taking  the  reading. 


FIG.  45. 

Volt-ammeter  for  Measuring  Both 
Pressure  and  Current.  Small 
Pocket  Form. 


FIG.  46. 

Stationary  Volt-ammeter  Which  Indi- 
cates the  Direction  of  Current  Flow. 
Apple  Electric  Company,  Dayton, 
Ohio. 


The  voltage  scale  is  graduated  in  only  one  direction  from  zero. 
In  Fig.  47  two  complete  instruments,  a  voltmeter  and  an 


FIG.  47- 
Ammeter  and  Voltmeter  Mounted  Together  Permanently. 

ammeter,  are  mounted  on  the  same  base.     They  can  both  be 
used  at  the  same  time,  and  used  continuously.     The  instrument 


ELECTRIC   MEASURING  INSTRUMENTS  59 

is  so  constructed  that  it  can  be  used  on  vehicles.  The  upper 
(middle)  terminal  is  connected  to  both  instruments.  The  right- 
hand  terminal  is  for  the  voltmeter  only,  and  the  left-hand  terminal 
is  for  the  ammeter  only. 

50.  "  Dead-beat  "  Indicating  Needle.  —  Unless  some  means 
is  provided  for  quickly  bringing  to  rest  the  indicating  needle  of 
a  voltmeter  or  an  ammeter,  the  needle  will  continue  vibrating 
for  a  considerable  time  after  the  current  is  first  sent  through  the 
instrument.  When  the  instrument  is  moved,  as  on  a  vehicle  or  in 
one's  hand,  the  needle  may  never  come  to  rest.  This  vibration 
of  the  needle  makes  it  impossible  to  take  an  accurate  reading. 

The  better  class  of  instruments  are  constructed  so  that  the 
needle  comes  to  rest  quickly  and  stands  almost  without  vibration 
even  when  the  entire  instrument  is  subjected  to  a  reasonable 
amount  of  motion,  yet  is  sensitive  in  its  movement  to  indicate 
variation  in  the  current  or  pressure.  Such  an  indicating  needle 
is  said  to  be  "  dead-beat."  This  dead-beat  effect  is  generally 
obtained  by  constructing  the  instrument  so  that  the  movement 
of  the  needle  and  its  attached  parts  set  up  foucault  currents  that 
in  turn  resist  the  movement  of  the  parts  to  which  the  needle  is 
attached.  This  damping  action  is  of  much  the  same  nature  in 
its  effect  as  that  which  can  be  obtained  in  a  stationary  instru- 
ment by  attaching  a  vane,  or  wing,  to  the  spindle  on  which  the 
needle  is  mounted,  and  submerging  the  vane  in  a  liquid. 


CHAPTER  VI. 
ELECTROMAGNETS. 

51.  Plain  Bar  Electromagnet.  —  If  an  insulated  wire  is 
wrapped  around  a  bar  of  iron  or  steel  as  shown  in  Fig.  48,  and 
a  direct  current  of  electricity  sent  through  the  wire,  the  bar  will 
become  a  magnet  and  remain  so  as  long  as  the  electricity  con- 
tinues flowing.  When  the  current  stops,  the  bar  will  lose  nearly 


c 


f 


c 


(B) 


FIG.  48. 
Electromagnets  of  Straight  Bar  Type. 

all  of  its  magnetism  if  it  is  of  commercially  pure  soft  iron  or 
steel.  A  small  amount  of  magnetism  will  remain.  This  is  called 
residual  magnetism.  If  the  bar  is  hardened,  or  tempered  like 
a  sewing  needle,  knitting  needle,  or  a  file  for  working  steel,  it 
will  retain  a  considerable  amount  of  magnetism  and  be,  for  a 
while  at  least,  a  permanent  magnet.  If  of  the  quality  and  con- 
dition of  steel  used  for  permanent  magnets,  it  will  remain  a  per- 
manent magnet  after  the  current  stops  and  the  bar  is  removed 
from  the  coil. 

If  the  current  flows  in  the  direction  indicated  by  the  arrow- 
heads on  the  wire,  then  the  upper,  or  top,  end  of  the  bar  will  be 

60 


ELECTROMAGNETS 


61 


a  north  pole,  and  the  lower  end,  or  bottom,  of  the  bar  a  south 
pole.  This  applies  to  both  (A)  and  (B)  in  the  figure.  If  the 
current  is  made  to  flow  in  the  opposite  direction  from  that  indi- 
cated, then  the  lower  end  of  the  bar  will  be  a  north  pole,  and 
upper  end  a  south  pole.  The  magnetic  flux  in  the  bar  is  from  the 
south  pole  to  the  north  pole. 

If  the  bar  is  held  before  the  dial  of  a  clock  with  one  end  point- 
ing toward  the  dial,  and  current  is  flowing  through  the  wire  in 
the  direction  of  rotation  of  the  hands  of  the  clock,  then  the  lines 
of  magnetic  force  will  flow  through  the  bar  toward  the  clock. 
The  north  pole  will  be  next  to  the  clock. 

Another  method  of  determining  which  is  the  north  pole  is  as 
follows:  If  the  bar  is  vertical  and  the  current  in  the  portion  of 
the  coil  between  the  observer  and  the  bar 
flows  east  while   the  observer  is  looking 
north,  then  the  north  pole  is  at  the  top. 
If  the  bar  is  horizontal  at  the  level  of  the 
observer's  eyes,  and  the  current  in  the  por- 
tion of  the  wire  between  the  observer  and 
the  bar  flows  downward,  then  the  north  pole 
is  at  the  right-hand  end. 

52.  Plunger-core  Electromagnet.  —  Fig. 
49  shows  a  non-magnetic  spool  i  with  a 
coil  2  of  insulated  wire  wound  around  it.  It 
may  be  assumed  that  the  coil  is  supported 
in  a  vertical  position.  An  iron  or  steel  bar 
3  is  shown  with  its  upper  end  projecting  a 
slight  distance  into  the  opening  through 
the  spool.  It  may  also  be  assumed  that  no 
current  is  passing  through  the  coil,  and  that  the  bar  is  resting 
on  some  support,  such  as  a  table. 

If  an  electric  current,  sufficiently  large,  is  passed  through  the 
coil,  the  core  will  be  drawn  up  into  the  spool  and  will  remain 
suspended  there  as  long  as  the  current  continues  flowing  through 
the  coil.  The  bar  will  remain  in  the  central  part  of  the  spool 
opening  without  touching  any  part.  Its  middle  will  be  somewhat 
below  the  middle  of  the  coil,  on  account  of  the  weight  of  the  bar. 


FIG.  49. 

Electromagnet  with 
Plunger  Core. 


62 


ELECTRIC  IGNITION 


As  soon  as  the  current  is  stopped  the  bar  will  fall.     The  current 

must  be  direct  (not  alternating). 

As  indicating  the  force  with  which  the  bar  is  drawn  upward,  it 

can  be  shot  up  completely  through 
and  above  the  spool  if  the  current 
is  stopped  while  the  bar  is  still 
moving  rapidly  upward  just  after 
the  circuit  has  been  closed. 

53.  U-shaped  Electromagnet.  - 
Fig.  50  shows  an  electromagnet 
shaped  like  the  letter  U  in  an  in- 
verted position.  When  a  direct 
current  flows  through  the  winding 
as  indicated  by  the  arrowheads, 
the  poles  are  N  and  S,  according 
FIG>  5a  to  the  marking  on  the  bar  in 

U-shaped  Electromagnet.  the    %ure*      If    the    current     flows 

in   the  opposite  direction,  the  po- 
larity of  the  poles  is  changed. 

It  can  be  seen  that,  when  looking  at  the  ends  of  the  bar,  the 


FIG.  51. 

Ring  Electromagnet  with  Consequent  Poles. 

current  flows  clockwise  around  the  south-pole  leg  of  the  bar, 
and  counter-clockwise  around  the  north-pole  leg  of  the  bar.     The 


ELECTROMAGNETS 


winding  is  as  if  the  whole  coil  had  been  wound  on  a  straight 
bar,  and  the  bar  then  bent  to  the  U-form. 


FIG.  52. 
Ring  Electromagnet  with  Two  Projecting  Poles. 


FIG.  53- 
Four-pole  Ring-shaped  Electromagnet. 

By  attaching  suitably  formed  pole-pieces  to  the  ends  of  the 
bent  bar,  it  can  be  used  for  furnishing  the  magnetic  field  of  an 
electric  generator. 


64  ELECTRIC  IGNITION 

54.  Ring-shaped  Electromagnet  with  Consequent  Poles.  —  A 

plain  ring  of  iron  or  steel  can  be  magnetized  electrically  so  as  to 
make  a  north  pole  and  south  pole  as  indicated  in  Fig.  51.  The 
manner  of  winding  the  coil  and  the  direction  of  current  are 
indicated  in  the  figure.  Poles  located  in  this  manner  are  called 
consequent  poles. 

By  attaching  suitable  pole-pieces  to  the  ring,  one  at  N  and 
another  at  S,  it  can  be  used  for  the  field-magnet  of  an  electric 
generator. 

55.  A  bipolar  ring-shaped  electromagnet  with  winding  on 
pole-pieces  is  shown  in  Fig.  52.     The  pole-pieces  may  be  either 
an  integral  part  of  the  ring,  or  separate  parts  attached  to  the 
ring  by  bolts  or  other  suitable  fastenings. 

56.  A  four-pole  ring-shaped  electromagnet  is  shown  in  Fig.  53. 
A  magnetizing  coil  is  wound  on  each  pole-piece.     The  direction 
of  the  current  through  each  coil  is  indicated  by  the  arrowheads. 


CHAPTER  VII. 
DIRECT-CURRENT  GENERATORS  WITH  ELECTROMAGNETS. 

57.  General.  —  Electromagnets  can  be  used  in  conjunction 
with  either  an  armature  that  delivers  an  alternating  current,  one 
that  delivers  a  direct  current,  or  one  that  delivers  both  direct 
and   alternating   current.     When   the   armature   delivers   only 
alternating  current,  some  auxiliary  source  of  direct  current  must 
be  provided  for  supplying  electricity  to  magnetize  the  field- 
magnets;  in  other  words,  for  exciting  the  field.     But  when  the 
armature  delivers  direct  current,  all  or  part  of  the  current  can 
be  used  to  excite  the  field-magnets,  thus  eliminating  the  necessity 
of  the  auxiliary  source  of  current  supply. 

It  is  believed  that  the  only  type  of  electromagnetic  generators 
that  are  used  for  ignition  purposes  is  that  in  which  the  armature 
delivers  direct  current,  therefore  only  this  type  will  be  described. 

Shunt-wound  Direct-current  Generators. 

58.  A  bipolar  direct-current  generator  with  U-shaped  shunt- 
wound  electromagnets  is  shown  in  elementary  form  in  Fig.  54. 
Two  circuits  are  connected  to  the  brushes,  one  through  the 
external  circuit  i,  and  the  other  through  the  field-coils  2  and  3. 
The  latter  is  called  a  shunt  circuit,  or  simply  a  shunt.     The 
shunt  is  a  comparatively  small  wire  of  considerable  length  and 
a  great  number  of  turns  around  the  magnet  core,  so  that  only 
a  small  proportion  of  the  current  that  the  armature  is  able  to 
deliver  passes  through  the  field-coils.* 

*  The  amount  of  direct  continuous  current  that  flows  steadily  through  a  wire 
is  inversely  proportional  to  the  length,  and  directly  proportional  to  the  sectional 
area  of  the  wire.  A  thin  wire  offers  more  resistance  to  the  flow  of  current  through 
it  than  a  thick  wire  of  the  same  material.  This  is  analogous  to  the  greater  resist- 
ance offered  to  the  flow  of  a  liquid  through  a  small  pipe  than  through  a  large  one. 
The  resistance  offered  to  flow  in  both  the  wire  and  the  pipe  is  proportional  to  the 
length  of  the  wire  and  the  pipe. 

65 


66 


ELECTRIC  IGNITION 


A  generator  of  this  nature  must  first  have  its  field-magnets 
magnetized  by  current  from  an  exterior  source,  or  by  another 
magnet.  After  being  once  magnetized,  the  field-magnets  retain 
enough  residual  magnetism  to  start  the  generation  of  a  current 
in  the  armature  when  it  is  rotated,  unless  the  magnets  are  sub- 
jected to  some  unusual  demagnetizing  influence. 

When  the  armature  is  started  to  rotate,  the  slight  electro- 
motive force  generated  by  the  residual  magnetism  in  the  field- 


FIG.  54. 

Bipolar  Direct-current  Electric  Generator  with  Shunt-wound  U-shaped  Electro- 
magnets. 

magnets  sends  a  correspondingly  small  current  through  the  field- 
coils.  This  current  strengthens  the  magnets,  which  in  turn 
induce  a  greater  electromotive  force  in  the  armature,  and  more 
current  flows  through  the  field-coils.  By  this  progressive  action, 
the  generator  "  picks  up  "  or  "  builds  up  "  its  magnetism  until  a 
condition  is  reached  where  the  increase  of  magnetism  becomes 
slow  in  relation  to  the  increase  of  current  in  the  field-coils,  and  a 
constant  electromotive  force  is  then  maintained  as  long  as  the 
external  circuit  remains  the  same. 


DIRECT-CURRENT  GENERATORS  WITH  ELECTROMAGNETS    67 

An  increase  of  current  through  the  external  circuit,  such  as 
may  be  caused  by  removing  a  piece  of  apparatus  from  it,  still 
leaving  the  circuit  closed,  causes  a  reduction  of  voltage  at  the 
brushes  of  the  generator. 

The  generator  is  usually  so  constructed  for  ignition  purposes 
that  the  variation  of  pressure  at  the  brushes  is  not  excessive 
for  variations  of  current  within  the  range  through  which  the 
machine  is  designed  to  operate.  A  method  of  preventing  this 


FIG.  55. 

Shunt-wound  Direct-current  Electric  Generator  with  Ring-shaped  Bipolar  Field- 
magnets. 

drop  of  pressure  at  the  brushes,  by  using  a  "  compound  winding  " 
on  the  magnets,  is  given  later. 

59.  A  bipolar  direct-current  generator  with  ring-shaped 
shunt- wound  electromagnets  is  shown  conventionally  in  Fig.  55. 
The  principle  of  operation  is  the  same  as  for  the  generator  shown 
in  the  preceding  figure.  It  may  be  noted,  however,  that  the 
brushes  do  not  stand  in  the  same  position  relative  to  the  pole- 
pieces  as  they  do  in  the  former  figure.  In  Fig.  54  the  position 
of  the  brushes  relative  to  the  pole-pieces  corresponds  to  that  in 
Fig.  37.  In  order  to  obtain  the  relative  positions  shown  in 
Fig.  55,  the  commutator  in  Fig.  37  may  be  twisted  around  a 
quarter-turn  counter-clockwise  relative  to  the  armature  core 


68 


ELECTRIC  IGNITION 


without  changing  the  connections  of  the  wires  to  the  commutator. 
In  any  case,  the  brushes  can  be  made  to  stand  in  any  position 
relative  to  the  pole-pieces,  by  making  the  connections  to  the 
commutator  segments  accordingly. 

A  complete  commercial  machine  of  the  type  shown  conven- 
tionally in  Fig.  55  is  illustrated  in  Fig.  56.     The  protective  cap 


FIG.  56. 
(See  also  Figs.  57,  58,  59,  and  60.) 

Bipolar  Direct-current  Electromagnetic  Generator.     The  Dayton  Electric  Manu- 
facturing Co.     Dimensions  in  inches:  io|  long;  5!  wide;  5!  high. 

r  3  amperes  continuously. 
Capacity  •<    8  volts  at  1000  r.p.m. 
1 10  volts  at  1 200  r.p.m. 


1.  Commutator. 

2.  Brush,  insulated. 

3.  Brush  spring,  insulated  at  end  that 

presses  against  brush. 

4.  Terminal. 

5.  Connection    between    brush    and 

terminal  4. 


6.  Field  Coil. 

7.  Steel  tube  around  armature. 

(Discarded  in  later  designs.) 

8.  Oiler  with  felt  wick. 

9.  Spider  with  bearing  for  armature 

spindle  and  with  brush-holders. 


is  opened  out  on  a  hinge  at  the  commutator  end  to  show  the 
working  parts.  The  pole-pieces  are  above  and  below  the  arma- 
ture. The  brushes  are  perpendicular  to  the  commutator,  so 
the  armature  can  rotate  in  either  direction.  Each  brush  has 
a  short  ribbon  spring,  somewhat  like  a  short  clock-spring,  for 


DIRECT-CURRENT   GENERATORS   WITH   ELECTROMAGNETS      69 


pressing  it  against  the  commutator.  The  magnetizing  coil  6  of 
the  top  pole-piece  is  partly  visible.  At  7  is  a  steel  tube  which 
fits  against  the  pole-pieces,  and  inside  of 
which  the  armature  runs  without  touching 
it.  The  use  of  this  tube  has  been  discon- 
tinued in  later  designs. 

The  armature  for  this  machine  is  shown 
separately  in  Fig.  35.  The  oiling  device  is 
shown  in  Fig.  57.  It  consists  of  an  oil  res- 
ervoir into  the  top  of  which  is  fitted  a 
round  felt  wick  that  is  pressed  up  against 
the  journal  of  the  armature  shaft  by  a  coiled 
compression  spring.  The  capillary  action  of 


FIG.  57. 


.,          .  ,  ,,          .,  ,,       ,  Oiling  Device  with  Felt 

the  wick  carries  the  oil  up  to  the  bearing       wkk?  for  Fig  s6 
gradually.      The    field-coils    are   shown   in 
Fig.  58.     Each  coil  is  made  up  of  insulated  wire  which,  after 
being  wound  to  form,  has  air  and  moisture  removed  by  placing 
it  in  a  vacuum,  and  is  then  insulated  by  impregnating  it  with 


FIG.  58. 
Field-Coils,  for  Fig.  56. 


liquid  insulating  compound  that  hardens  like  varnish  upon  dry- 
ing. The  coil  is  then  wound  with  insulating  tape.  The  brushes, 
Fig.  59,  are  of  graphite  with  a  bronze-gauze  core.  The  terminal 
wires  are  soldered  to  the  gauze  core. 


ELECTRIC  IGNITION 


Fig.  60  shows  the  spider  10  which  supports  the  brushes  and 
the  commutator  end  of  the  armature  spindle. 

The  capacity  of  a  machine  like  that  in  Fig.  56,  having  the 
dimensions:  i of  inches  long,  5!  inches  wide,  and  5!  inches  high, 


FIG.  59. 
Commutator  Brushes,  for  Fig.  56. 

as  rated  by  the  makers,  is  3  amperes  of  steady  current  at  a  pres- 
sure of  8  volts  when  running  at  1000  r.p.m.,  or  a  little  more  than 
12  volts  at  1200  r.p.m. 


FIG.  60. 
Bearing,  Brushes,  Oiler,  etc.,  for  Fig.  56. 

The  only  means  of  regulating  the  pressure  is  by  variation  of 
the  speed.  The  current  is  also  varied  in  practically  the  same 
proportion  as  the  pressure  when  the  circuit  remains  unchanged. 
A  friction  pulley  or  a  belt  pulley  combined  with  a  speed  governor 
is  provided  with  the  machine. 


DIRECT-CURRENT   GENERATORS  WITH  ELECTROMAGNETS      71 

60.  A  four-pole  direct-current  generator  with  shunt-wound 
electromagnets  is  shown  diagrammatically  in  Fig.  61.  Only  two 
brushes  are  used.  They  are  placed  at  an  angle  of  90  degrees 
with  each  other  of  necessity.  The  path  and  direction  of  mag- 
netic flux  is  indicated  by  the  broken  lines  with  double  arrow- 
heads on  them. 

The  connections  for  an  armature  of  a  four-pole  machine  with 
two  brushes  are  shown  in  Fig.  62.  This  armature  has  twenty- 


FIG.  61. 

Elementary  Four-pole  Direct-current  Electric  Generator  with  Shunt-wound 

Magnets. 

one  coils  and  the  same  number  of  commutator  segments,  or 
strips.  The  broken  lines  indicate  the  part  of  the  winding  that 
is  in  the  rear  of  the  armature  core.  The  core  is  not  shown, 
since  it  would  detract  from  the  clearness  of  the  diagram.  When 
the  direction  of  rotation  is  clockwise,  as  indicated  by  the  feathered 
arrow,  the  flow  of  current  is  as  indicated  by  the  arrowheads  on 
the  lines. 

Figs.  63  and  64  show  a  direct-current  shunt-wound  four-pole 
generator  with  two  brushes.  The  former  figure  is  partly  in  sec- 
tion. A  governor  spring  bears  against  the  commutator  end  of 
the  armature  shaft  and  presses  the  friction  pulley  against  the 
flywheel  that  drives  it.  A  speed  governor  is  located  on  the 


72  ELECTRIC  IGNITION 

shaft  between  the  friction  pulley  and  the  armature.  This  gover- 
nor moves  the  entire  armature  and  the  friction  pulley  endwise 
as  the  speed  increases,  so  as  to  reduce  the  pressure  of  the  friction 
pulley  against  the  flywheel,  thus  allowing  the  friction  pulley 


FIG.  62. 

Armature  Connections  for  Drum  Armature  with  Twenty-one  Coils  and  the  Same 
Number  of  Commutator  Segments.     For  Four-pole  Field-Magnets. 

to  slip  on  the  flywheel  and  limiting  the  speed  to  the  desired 
rate.  An  adjusting  screw  is  provided  for  varying  the  pressure 
of  the  governor  spring  against  the  end  of  the  shaft  so  as  to  obtain 
the  desired  speed  limit. 

There  are  two  brushes  set  at  90  degrees  with  each  other.     They 
are  a  combination  of  wire  gauze  and  graphite.     The  armature 


DIRECT-CURRENT   GENERATORS  WITH  ELECTROMAGNETS      73 


has  twenty-one  coils  and  the  same  number  of  segments  in  the 
commutator.    The  frame  of  the  generator,  which  is  also  the 


GOVERNOR 

FIBRE  THRUSTWASHER 
BEARING 

FRICTION 
PUUIY 


COHMUTATOR 


FIG.  63.     (See  also  Fig.  64.) 

Four-pole  Direct-current  Electric  Generator.     Sectional  View.     Apple  Electric 
Company,  Dayton,  Ohio. 

magnet  ring,  is  cast  from  semi-steel.     This  is  a  material  between 
soft  steel  and  cast-iron  in  its  physical  and  magnetic  properties. 

The  generator  is  provided  with  an  automatic  cut-out  for  open- 
ing and  closing  the  circuit  when  used  in  connection  with  storage 


COVERNORjSPRING 
ADJUSTER 

BRUSH    SPRING 
4KIU3TER 


BRUSHES 


GOVERNOR-  SPRING 


PRESSED  STEEL  LID 


AUTOMATIC'CUTOUT    'OIL  CL)P     LINE.WlRt.f  BINDING.  POST 

FIG.  64.     (See  also  Fig.  63.) 
Commutator  End  of  Four-pole  Direct-current  Electric  Generator. 

batteries.  This  method  of  using  is  described  later  in  connection 
with  a  complete  ignition  system  (see  Fig.  95  and  several  follow- 
ing figures).  The  machine  is  also  equipped  with  a  device  for 
keeping  the  current  nearly  constant  when  the  speed  of  the 


74 


ELECTRIC  IGNITION 


armature  is  variable.     This  device  automatically  changes  the 
amount  of  resistance  in  the  field  circuit. 

Compound-wound  Direct-current  Generators. 

61.  Series-and-shunt  Field  Winding.  —  It  is  often  desirable 
to  have  a  generator  that  will  keep  the  voltage  at  the  brushes 
practically  constant  when  the  rotative  speed  of  the  generator  is 
constant,  so  that  the  pressure  will  be  practically  constant  whether 


FIG.  65. 
Compound-wound  Direct-current  Electric  Generator. 

the  amount  of  current  delivered  is  variable  or  constant.  This 
is  accomplished  by  means  of  a  double  winding  on  the  field-mag- 
nets. One  of  the  windings  is  the  regular  shunt  winding,  and 
the  other  winding  carries  the  current  that  flows  through  the 
external  circuit.  The  latter  is  called  the  series  winding.  Fig.  65 
shows  diagrammatically  a  generator  with  compound  field  winding 
of  this  nature. 

The  currents  in  both  windings  flow  in  the  same  direction 
around  the  magnet  cores.  It  has  been  explained  that  the  voltage 
at  the  brushes  drops  as  the  external  current  increases  when  only 


DIRECT-CURRENT   GENERATORS   WITH   ELECTROMAGNETS      75 

a  shunt  winding  is  used.  This  tendency  is  counteracted  by  the 
magnetizing  effect  of  the  current  which  flows  through  the  series 
coil.  The  magnetizing  effect  of  the  series  coil  increases  as  the 
current  through  the  series  coil  and  external  circuit  increases. 
By  giving  the  series  coil  a  suitable  number  of  turns  around  the 
magnet  core,  the  voltage  at  the  brushes  can  be  kept  almost 
constant  in  a  properly  designed  machine.  By  giving  the  series 


FIG.  66. 
Rheostat  in  Shunt-coil  Circuit  of  Electric  Generator. 


coil  more  than  this  number  of  turns,  the  voltage  can  be  made 
to  rise  as  the  current  in  the  external  circuit  increases.  This 
over-compounding  is  often  desirable. 

The  voltage  of  a  compound-wound  machine  such  as  shown  in 
Fig.  65  is  approximately  proportional  to  the  speed  of  the  arma- 
ture, within  the  range  of  speed  at  which  the  machine  is  designed 
to  operate. 

62.  Field  Rheostat  for  Regulating  Voltage.  —  When  the  rota- 
tive speed  of  the  armature  of  an  electromagnetic  generator  is 
constant,  the  voltage  at  the  brushes  can  be  regulated  by  varying 


76  ELECTRIC  IGNITION 

the  electrical  resistance  of  the  shunt-coil  circuit.  The  usual 
means  of  doing  this  is  a  rheostat. 

Fig.  66  shows  a  compound-wound  generator  with  an  elemen- 
tary form  of  rheostat  in  the  shunt  circuit.  The  principal  parts 
of  the  rheostat  are  shown  at  A  and  R.  R  is  a  series  of  coils  of 
wire.  The  ends  of  the  wire  are  connected  to  metal  contact- 
points  i,  2,  3,  4,  and  5.  These  points  are  arranged  in  an  arc 
of  a  circle.  A  switch-arm  A  is  pivoted  at  the  center  of  the  arc 
and  is  of  such  a  form  that  it  can  be  moved  into  contact  with  any 
of  the  contact-points  just  enumerated.  This  rheostat  is  inter- 
posed in  the  shunt  circuit  by  cutting  the  shunt  wire  at  any  con- 
venient point  and  connecting  the  wire-ends  thus  obtained  to  the 
rheostat  as  shown.  One  end  is  connected  to  the  contact-point 
i,  and  the  other  end  to  the  pivot  of  the  arm  A. 

When  the  rheostat  arm  A  is  set  in  contact  with  point  4  as 
shown,  the  shunt  current  must  pass  through  the  rheostat  coils 
that  lie  between  i  and  4,  and  the  resistance  of  these  coils  is 
added  to  that  of  the  field-coils.  The  current  that  flows  through 
the  field-coils  is  therefore  less  than  would  flow  if  the  rheostat 
were  not  in  the  circuit,  and  the  voltage  at  the  brushes  is  in  con- 
sequence less  than  it  would  be  without  the  rheostat.  By  moving 
the  arm  into  contact  with  either  3,  2,  or  i,  the  voltage  can  be 
increased;  or  by  moving  it  to  5,  the  voltage  can  be  decreased. 

The  swinging  end  of  the  contact  arm  A  is  wide  enough  to 
touch  two  of  the  contact-points  at  the  same  time  when  moving 
from  one  to  another.  This  is  necessary  in  order  to  prevent 
breaking  the  circuit  while  varying  the  resistance  in  the  circuit. 

The  rheostat  is  generally  a  separate  piece  of  apparatus.  The 
resistance  wire  used  in  it  is  ordinarily  of  a  material  that  has  high 
electric  resistance  compared  with  that  of  copper. 

A  rheostat  can  be  used  in  the  field  circuit  of  a  plain  shunt- 
wound  machine  as  well  as  in  one  that  is  compound- wound. 

Reversing  the  Rotation  of  the  Armature. 

63.  Most  of  the  generators  for  ignition  usage  have  the  brushes 
perpendicular  to  the  commutator  so  that  the  armature  can  be 
rotated  in  either  direction  without  injury. 


DIRECT-CURRENT   GENERATORS  WITH  ELECTROMAGNETS      77 

The  field-coil  connections  to  the  brushes  must  be  interchanged 
when  the  direction  of  rotation  of  the  armature  is  to  be  reversed. 
If  the  armature  is  run  in  the  new  direction  without  making  this 
change  of  connections,  it  will  not  pick  up  its  magnetism  and 
generate  a  current.  This  is  because  the  different  direction  of 
rotation  changes  the  polarity  of  the  brushes,  so  that  the  one 
formerly  positive  becomes  negative,  and  the  former  negative 
one  becomes  positive.  The  current  which  is  generated  by  the 
residual  magnetism  therefore  flows  through  the  field-coils  in 
the  direction  to  demagnetize  them  instead  of  strengthen  their 
magnetism.  The  result  is  that  no  appreciable  pressure  is  gen- 
erated, and  of  course  no  appreciable  current  can  be  obtained 
without  corresponding  pressure. 


CHAPTER  VIII. 

PRIMARY  BATTERIES. 

Carbon-zinc  Battery. 

64.  When  an  electric  battery  is  subject  to  considerable  motion, 
as  in  automobiles,  railway  motor  cars,  and  motor  boats,  a  "  dry 
battery  "  is  almost  exclusively  used  if  ignition  current  is  supplied 
by  a  primary  battery.  The  dry  primary  battery  is  also  much 
used  for  ignition  in  stationary  motors. 

Only  one  of  almost  innumerable  types  of  dry  batteries,  as 
distinguished   by  the  substances  used    in   them,  is  used   to  a 
noticeable  extent.     In  this  commonly  used  battery  the  substances 
_^  which     designate     it     are     carbon, 

zinc,  and  sal  ammoniac  (also  called 
ammonium  chloride,  NH4C1) .  Other 
substances  are  used  in  connection 
with  these  and  are  essential  to  its 
operation  for  supplying  current  for 
motor  ignition.  In  order  to  make 
clear  the  nature  of  this  battery  cell 
and  its  operation,  the  elementary 
form  using  only  carbon,  zinc,  and 
sal  ammoniac  will  be  first  described. 
65.  Elementary  Leclanche  Car- 
bon-zinc Wet  Cell.  —  A  bar  of  zinc 

and  a  slab  of  carbon  immersed  in  a 
FIG.  67. 

Elementary  Wet  Electric  Battery  Solution  °f  Sal  ammoniac  in  a  glass 

Cell.  vessel  are  shown  in  Fig.  67.      The 

solution  is  made  by  dissolving   sal 

ammoniac  (a  white  salt)  in  water.*     The  carbon  and  zinc  are 
connected  together  by  a  wire. 

*  One-quarter  pound  of  sal  ammoniac  to  a  quart  of  water  is  the  proportion 
generally  used  in  a  cell. 

78 


PRIMARY  BATTERIES  79 

A  current  of  electricity  begins  to  flow  from  the  carbon  to  the 
zinc  through  the  wire  as  soon  as  the  carbon  and  zinc  are  immersed 
in  the  solution.  The  current  also  flows  through  the  solution 
from  the  zinc  to  the  carbon  inside  of  the  cell.  The  amount  of 
current  decreases  very  rapidly  immediately,  and  then  continues 
to  decrease  at  a  slower  rate  till,  after  considerable  time,  there  is 
scarcely  a  perceptible  flow.  The  cause  of  the  decrease  of  current 
is  called  polarization,  and  is  described  below. 

Decrease  of  current  on  account  of  polarization  also  occurs 
in  this  elementary  form  of  cell  when  it  is  used  in  the  manner 
required  for  motor  ignition.  This  action  makes  it  unsuitable 
for  motor  ignition  purposes. 

The  electric  current  through  the  wire  is  generated  by  chemical 
action  between  the  zinc  and  the  solution.  The  solution  attacks 
the  zinc  and  combines  with  it.  This  action  dissolves,  corrodes, 
or  eats  away  the  zinc. 

The  above  combination  is  called  a  primary  electric  cell.  In 
earlier  days  it  was  commonly  called  a  galvanic  cell  or  a  voltaic 
cell.  Two  or  more  such  cells  properly  connected  together  form  a 
battery  of  cells,  called  an  electric  battery.  In  commercial  usage 
a  single  cell  is  generally  also  called  a  battery. 

The  carbon  and  zinc  are  called  the  electrodes,  and  the  solu- 
tion is  called  the  electrolyte.  All  three  together  are  called  the 
active  elements  of  the  cell. 

The  point  at  which  the  wire  is  attached  to  the  carbon  is  the 
positive  (+)  terminal  of  the  cell;  and  the  point  of  attachment  of 
the  wire  to  the  zinc  is  the  negative  (  — )  terminal  of  the  cell.* 

In  commercial  forms  of  cells,  binding  screws  and  nuts,  or 
other  suitable  fastenings,  are  usually  provided  for  attaching 
wires  at  the  terminals. 

If  the  wire  is  cut  in  two  and  the  ends  separated,  the  flow  of 
current  through  it  is  stopped.  The  chemical  action  in  the  cell 


*  On  account  of  the  confusion  which  arises  when  one  of  the  elements  of  the 
cell  is  referred  to  as  the  positive  electrode,  and  the  other  as  the  negative  electrode, 
the  terms  positive  electrode  and  negative  electrode  are  not  used  herein  in  con- 
nection with  electric  cells  and  batteries.  The  terms  anode  and  cathode  are  omitted 
in  connection  with  batteries  for  the  same  reason. 


8o  ELECTRIC  IGNITION 

also  stops  with  the  stoppage  of  current  through  the  wire,  except 
that  there  is  generally  some  slight  amount  of  local  action  on  the 
zinc.  Impurities  in  the  zinc,  such  as  iron  and  copper,  increase 
this  local  action.  But  even  if  the  zinc  is  very  pure,  local  action 
will  still  occur  on  account  of  a  difference  in  the  strength,  or 
quality,  of  the  portion  of  the  solution  at  the  top  and  that  at 
the  bottom.  The  local  action  due  to  this  latter  cause  eats  away 
the  zinc  at  and  near  the  surface  of  the  solution.  Local  currents 
through  the  zinc  are  caused  by  this  action. 

The  electromotive  force  of  a  primary  cell  with  carbon  and 
zinc  electrodes  in  sal-ammoniac  solution  is  slightly  less  than 
1.5  volts  between  the  terminals  after  the  cell  has  not  been  de- 
livering current  for  some  time.  The  voltage  drops  as  soon  as 
the  circuit  is  closed  and  current  begins  to  flow.  It  slowly  rises 
again  to  its  full  value  after  the  current  is  stopped  by  opening 
the  circuit. 

66.  Polarization  of  Primary  Electric  Cell.  —  The  decrease  of 
current  that  occurs  while  the  circuit  of  a  cell  is  kept  closed,  in 
the  case  of  a  cell  having  only  the  elements  carbon,  zinc,  and  sal 
ammoniac,  is  due  to  the  formation  of  hydrogen  gas  by  the 
chemical  action.     The  gas  collects  on  the  carbon  and  retards 
chemical  action.     This  retardation  is  apparently  chiefly  due  to 
a  counter-electromotive  force  which  the  hydrogen  sets  up,  and 
also  partly  due,  but  to  a  less  extent,  to  the  formation  of  bubbles 
on  the  carbon  so  as  to  prevent  the  electrolyte  from  having  as 
good  contact  with  the  carbon  as  it  has  before  any  bubbles  are 
formed.     If  the  carbon  is  molded  very  dense  and  has  a  very 
smooth  surface,  polarization  can  be  at  least  largely  prevented  by 
constantly  brushing  off  the  bubbles  of  hydrogen.     This  is  not 
practicable,  however.     The  usual  method  is  to  prevent  polariza- 
tion by  chemical  means.     This  is  ordinarily  called  depolariza- 
tion.    It  is  successfully  applied  to  both  wet  cells  and  dry  cells. 

67.  A  dry  cell  with  carbon  and  zinc  electrodes  and  chemical 
depolarizer  is  shown  sectionally  in  Fig.  68.     This  is  the  type  of 
dry  cell  that  is  almost  universally  used  for  ignition  where  the 
battery  is  subjected  to  much  motion. 

The  containing  vessel,  cup,  or  can  i  is  made  of  sheet  zinc  and 


PRIMARY  BATTERIES 


8l 


is  one  of  the  electrodes.  The  can  is  lined  with  absorbent  paper  2 
(blotting  paper)  that  is  saturated  with  water  in  which  sal  ammo- 
niac and  zinc  chloride  have  been  dissolved.  In  the  center  is  a 
molded  bar  of  carbon  3  around  which  is  packed  a  mixture  4  of 
manganese  dioxide  (MnO2)  and  car- 
bon dust.  The  manganese  dioxide 
is  in  granular  form  (powder) .  The 
paper  is  turned  in  over  the  top  of 
the  mixture  so  as  to  cover  it  nearly 
or  completely.  On  top  of  the  paper 
is  a  little  sawdust  or  sand,  and  above 
this  a  sealing  compound  5,  composed 
chiefly  of  pitch,  to  make  the  cell 
water-tight.  The  absorbent  paper 
and  the  mixture  around  the  bar  are 
saturated  with  the  electrolyte  before 
the  cell  is  sealed.  The  carbon  in 
the  mixture  is  generally  coke-dust, 
and  the  carbon  bar  is  made  of  coke- 
dust  mixed  with  a  binder  such  as 
pitch.  The  plastic  mixture  for  the 
bar  is  molded  to  form  and  then 
baked  to  give  it  strength  and  at  the 
same  time  convert  the  binder  into 
carbon.  Carbon  is  a  better  con- 
ductor of  electricity  than  manganese 
dioxide,  hence  mixing  it  with  the  manganese  dioxide  gives  the 
cell  less  resistance  to  the  flow  of  electricity  than  if  manganese 
dioxide  alone  were  used  around  the  bar.  A  low  resistance  is 
desirable  in  a  dry  cell,  especially  one  that  is  to  be  used  for 
gas-engine  ignition. 

The  carbon  bar  is  capped  with  a  tight-fitting  brass  piece  which 
has  a  binding  screw  and  nut.  Another  binding  screw  is  soldered 
to  the  top  of  the  zinc  can.  The  cap  on  the  carbon  bar  at  the 
center  of  the  cell  is  the  positive  (+)  terminal,  and  the  binding 
screw  fastened  to  the  zinc  can  is  the  negative  (— )  terminal. 

The  manganese  dioxide  is  a  depolarizer.     It  gives  up  oxygen, 


FIG.  68. 
Dry  Cell  of  an  Electric  Battery. 


82  ELECTRIC  IGNITION 

which  combines  with  the  hydrogen  gas  that  is  liberated  by  the 
action  described  in  connection  with  the  elementary  carbon-zinc 
cell.  The  hydrogen  and  oxygen  combine  in  the  proportion  to 
form  water,  which  is  a  liquid  and  remains  in  the  cell. 

The  electromotive  force  of  a  dry  cell  of  the  kind  just  described 
is  about  1.5  volts  on  open  circuit  when  new  and  in  good  condition, 
irrespective  of  the  size  of  the  cell.  A  large  cell  will  give  more 
current  than  a  small  one. 

The  size  of  dry  cell  which  has  become  standard  is  2\  by  6 
inches  long.  It  is  cylindrical  in  form.  The  cell  is  usually 
covered  with  some  insulating  material,  such  as  paper  or  straw- 
board,  except  the  terminals.  This  insulating  covering  prevents 
the  metal  of  one  cell  from  coming  into  contact  with  that  of 
another  when  the  cells  are  grouped  together  to  form  a  battery. 
A  cell  of  this  size  will  give  from  15  to  20  amperes  of  current 
through  a  low-resistance  ammeter  when  the  circuit  is  first  closed. 
The  cell  is  practically  short-circuited  when  its  terminals  are 
connected  through  a  low-resistance  ammeter,  the  resistance  of 
the  latter  being  about  the  same  as  that  of  a  short,  heavy  copper 
wire.  The  cell  will  deliver  this  maximum  amount  of  current 
during  only  a  few  seconds.  The  current  rapidly  decreases  when 
the  cell  is  short-circuited,  but  continues  with  constantly  de- 
creasing value  till  the  battery  is  exhausted. 

The  exhaustion  of  a  dry  cell  of  the  usual  construction  is 
due  to  weakening  of  the  liquid  electrolyte  with  which  the 
absorbent  paper  in  the  cell  is  saturated.  This  weakening  is  on 
account  of  the  chemical  action  necessary  to  produce  electric 
current. 

68.  Deterioration  of  new  permanently  sealed  dry  batteries 
often  occurs  to  a  marked  extent  before  they  are  put  into  use. 
They  sometimes  deteriorate  in  a  few  months  or  less  of  storage  so 
as  to  become  useless.     Such  rapid  deterioration  is  not  apt  to 
occur  in  well-made  cells  whose  materials  are  suitably  pure. 

69.  New  Type  of  Carbon-zinc  Dry  Cell,  not  Sealed.  —  A  type 
of  dry  cell  which  is  actually  and  thoroughly  dry  until  put  into 
use  was  first  exhibited  at  the  Atlanta  automobile  show  in  the 
latter  part  of  the  year   1909.     The  cell  resembles  in  general 


PRIMARY  BATTERIES  83 

appearance  and  construction  the  one  shown  in  Fig.  68,  except 
the  carbon  rod  and  the  terminal  on  it. 

The  carbon  rod  of  the  new  cell  is  made  hollow  and  is  provided 
with  a  wooden  stopper  at  the  open  end.  The  terminal  is  fastened 
to  one  side  of  the  top  of  the  carbon.  When  the  cell  is  manu- 
factured it  is  left  entirely  dry,  but  all  of  the  necessary  chemical 
elements  are  put  in  it.  It  is  chemically  inactive  and  does  not 
deteriorate  in  storage  before  putting  into  use. 

To  prepare  the  cell  for  use,  it  is  only  required  to  fill  the  hollow 
carbon  rod  with  water,  after  removing  the  stopper,  which  is 
replaced  after  the  water  is  poured  in.  The  water  dissolves  the 
chemical  elements  which  with  the  water  form  the  electrolyte. 
After  being  thus  put  into  operation,  the  cell  is  subject  to  ex- 
haustion and  deterioration  the  same  as  a  permanently  sealed  cell 
of  the  same  quality. 

70.  Exhaustion  and  Running  Down  of  Dry  Batteries  in  Ser- 
vice. —  The  chemical  action  in  the  cell  by  which  electric  current 
is  generated  of  course  consumes  the  active  materials  and  pro- 
duces new  chemicals.     The  result  is  a  dropping  off  of  the  activity 
of  the  cell  and  finally  its  exhaustion  to  such  an  extent  that  it 
becomes  useless. 

In  a  properly  constructed  cell,  the  chemical  elements  are  so 
proportioned  that  they  become  exhausted  at  about  the  same 
time.  The  zinc  cup  is  not  much  thicker  than  necessary  to 
furnish  the  requisite  metal  for  the  amount  of  chemicals  present. 
The  fact  that  the  zinc  is  sometimes  eaten  through  before  the 
cell  is  nearly  exhausted  is  an  indication  of  local  action  in  the  zinc, 
probably  on  account  of  impurities  in  the  metal.  Local  action 
is  more  apt  to  make  itself  known  when  the  battery  is  allowed 
to  stand  idle  during  a  considerable  portion  of  its  life. 

71.  Recuperation  of  dry  cells  can  generally  be  effected  by 
adding  sal-ammoniac   solution  to  the  inside  of  the   cell.     The 
solution  can  be  added  to  a  permanently  sealed  cell  by  making 
an  opening  through  the  sealing  compound  at  the  top  so  as  to 
expose  the  blotting  paper,  and  pouring  the  liquid  into  the  open- 
ing.    The  sealing  compound  can  be  readily  dug  out  with  a 
pointed  instrument.     It  is  not  necessary  to  replace  it,  since  the 


84  ELECTRIC  IGNITION 

cell  will  never  be  of  much  use  after  becoming  exhausted  the 
first  time.  This  expedient  of  recuperation  is  hardly  worth 
while  except  in  case  of  emergency. 

It  is  probable  that  the  new  type  of  unsealed  cell  described 
above  can  be  recuperated  by  pouring  in  a  solution  of  sal  ammoniac 
after  the  cell  has  been  run  down  in  service. 

The  addition  of  water  alone  will  sometimes  recuperate  a  cell 
slightly. 

Copper  Oxide  and  Zinc  Wet  Cell. 

72.  The  Lalande  and  Chaperon  wet  cell,  as  brought  out  in 
1881,  has  zinc  amalgamated  with  mercury  for  one  electrode,. and 
either  iron  or  copper  for  the  other.  The 
electrolyte  is  a  solution  of  either  caustic 
soda  (concentrated  lye,  sodium  hydrate, 
NaOH)  or  caustic  potash  (potassium  hy- 
drate, KOH).  A  depolarizer  of  copper 
oxide  (cupric  oxide,  CuO)  is  used.  Modi- 
fied forms  of  this  cell,  one  known  as  the 
Edison-Lalande  and  more  recently  as  the 
Edison  primary  battery,  and  the  latest  one 
,  v.  as  the  BSCO  battery,  are  used  to  a  consid- 

FIG.  69.     (See  also  Figs.  .        ... 

70  and  71.)  erable  extent  for  gas-engine  ignition,  espe- 

Copper  Oxide  and   Zinc  cially  for  stationary  engines. 

Wet  Cell.  Edison  Man-       73.   A  BSCO  wet  cell  is  shown  in  Fig. 

ufacturing    Company,  ,       Part  of  ^  contaming  vessel  is  broken 

Orange,  New  Jersey.  . 

away  to  show  the  interior  construction. 
The  electrodes,  depolarizer,  and  the  cover  of  the  cell  are  shown 
removed  from  the  cell  in  Figs.  70  and  71. 

The  copper  electrode  has  the  form  of  an  inverted  U-shaped, 
grooved,  or  channeled,  frame  A  which  hangs  from  the  cover  F 
of  the  cell,  the  connection  being  made  by  a  bolt  which  passes 
through  the  cover  and  has  thumbscrews  above  it.  The  depolar- 
izer slab  C  is  clamped  between  the  legs  of  the  copper  frame, 
which  are  drawn  together  against  the  beveled  edges  of  the  slab 
by  means  of  a  copper  cross-bar,  or  bridge,  D,  so  as  to  make  good 
electric  contact  between  the  copper  and  the  depolarizer  slab. 


PRIMARY  BATTERIES 


The  lower  ends  of  the  copper  frame  are  bent  in  under  the  slab 
to  support  it.  The  zinc  plates  B  are  suspended  from  the  cross- 
bar by  means  of  a  steel  bolt  which  passes  through  a  porcelain 
insulator  E  and  holds  the  zincs  firmly  in  place.  The  porcelain 
insulates  the  zincs  from  the  copper.  An  insulated  wire  is  con- 
nected to  the  zincs,  and  its  outer  free  end  is  the  negative  (— ) 


FIGS.  70  and  71. 
Elements  and  Top  of  Fig.  69. 

terminal  of  the  cell.  The  bolt  from  which  the  copper  frame  is 
suspended  is  the  positive  (+)  terminal. 

The  depolarizer  slab  is  a  mixture  of  copper  oxide  and  magne- 
sium chloride  compressed  to  form  in  molds  and  then  heated  to 
make  it  a  firm  mass.  The  magnesium  chloride  acts  only  as  a 
binder  to  hold  the  mass  together. 

The  zinc  plates  are  amalgamated  by  incorporating  about  two 
per  cent  of  mercury  with  them  when  they  are  cast. 

The  liquid  electrolyte  covers  the  zinc  plates  completely  to 
a  depth  of  an  inch  or  so  above  them.  A  layer  of  heavy  mineral 
oil  is  poured  on  the  electrolyte  and  floats  at  the  top  to  protect 
the  electrolyte  from  atmospheric  action.  If  air  is  allowed  to 
come  into  contact  with  the  electrolyte,  it  oxidizes  it  and  de- 
creases the  length  of  life  of  the  cell. 


86  ELECTRIC  IGNITION 

Since  the  rigid  parts  of  the  cell  are  firmly  fastened  together, 
the  cell  can  be  used  where  there  is  motion  without  danger  of  the 
electrodes  coming  into  contact  with  each  other  or  with  other 
parts  so  as  to  short-circuit  the  cell.  It  can  therefore  be  used  on 
vehicles  if  the  top  is  sealed  on,  for  which  provision  is  made  in 
one  type  of  the  cell  intended  for  ignition  use.  Cells  for  portable 
use  are  made  with  enameled  steel  containing  vessels,  or  jars. 

The  voltage  of  one  of  these  cells  on  open  circuit  is  slightly 
less  than  one  volt.  The  pressure  does  not  drop  much  below  one 
volt  during  use  until  the  battery  is  nearly  exhausted. 

The  renewals  for  an  exhausted  battery  consist  of  the  parts 
suspended  from  the  cover,  which  are  sent  out  as  a  unit  fastened 
together,  and  the  electrolyte  of  dry  caustic  potash  to  be  dissolved 
in  water.  The  oil  for  covering  the  electrolyte  may  also  be  in- 
cluded as  one  of  the  renewal  items.  Renewal  of  the  parts  is  made 
by  taking  out  the  bolt  which  passes  through  the  cover,  discard- 
ing the  copper  frame  and  parts  attached  to 
it,  and  fastening  the  new  frame  and  its 
attached  parts  in  place  with  the  old  cover- 
bolt;  also  discarding  the  exhausted  electro- 
lyte and  dissolving  the  new  in  water  poured 
into  the  jar. 

The  capacity  of  the  portable  cell  intended 
for  ignition  use  is  200  ampere-hours. 

74.   The  Edison  primary  battery,  already 
referred  to  as  an  earlier  form  of  the  one 
FlG-  72.  just  described,  differs  from  the  newer  form 

Early   form    of    Edison  only  in  mechanical  construction.      One  of 

Primary  Battery  shown     .  ...  .,     .       .  . 

in  Fig.  69.  these  earlier  cells  is  shown  in  Fig.  72,  with 

part  of  the  jar  broken  away  to  show  the 
interior.  The  zinc  plates  are  suspended  from  the  porcelain  cover, 
instead  of  from  the  copper  frame,  as  in  the  later  form,  and  the 
copper  frame  is  of  different  form,  with  a  bolt  connecting  the  two 
sides  under  the  depolarizer  slab.  The  zincs  are  not  so  firmly  and 
accurately  held  in  place  as  in  the  later  type  of  cell.  The  cell  is 
therefore  not  so  well  adapted  to  portable  use  as  the  latter 
type. 


PRIMARY  BATTERIES 


The  capacities  and  dimensions  of  some  of  these  cells  are  given 
in  the  following  table  according  to  the  Manufacturer's  rating: 


Diameter  and  Height  over  All.     Com- 
plete Cell  with 

Capacity  in 
Ampere-Hours. 

Porcelain  Jar. 

Enameled  Steel  Jar. 

Inches. 
4^X  7l 
SIX  8f 
7iXio| 

Inches. 
4*X  6f 
5lX  8 
7iXio 

IOO 
150 
300 

CHAPTER  IX. 

BATTERY  CONNECTIONS. 

75.  General.  —  In  order  to  obtain  suitable  electromotive  force 
and  current,  cells  are  connected  together  to  form  a  battery.     The 
best  arrangement  of  the  cell  with  regard  to  the  order  in  which 
their  terminals  are  connected  together  depends  on  the  nature  of 
the  service  to  be  performed  and  on  the  resistance  of  the  external 
circuit. 

In  the  following  discussion  it  is  assumed  that  all  of  the  cells 
in  a  battery  are  alike.  This  assumption  is  in  accordance  with 
the  best  practice.  Moreover,  the  discussion  relative  to  different 
kinds  and  capacities  of  cells  grouped  together  in  a  battery  is 
more  complicated  than  is  thought  should  be  presented  in  a  work 
of  this  nature. 

For  convenience  of  discussion,  it  will  be  assumed  that  either 
carbon-zinc  cells  or  copper-zinc  cells  are  used.  The  carbon  ter- 
minal, or  the  copper  terminal,  as  the  case  may  be,  is  the  positive 
one,  and  the  zinc  terminal  is  the  negative  one. 

Series-connected  Batteries. 

76.  A  series-connected  battery  of  four  cells,  all  alike,  is  shown 
in  Fig.  73.   -The  carbon  terminal  of  each  cell  is  connected  to  the 

Negative  Terminal-— ^.3^ 

of  Battery.  Zinc.  (jg)  \^6^  \  ^4^  \  ^-P  \-PositiveTerminal 

of  Battery. 

Carbon  or  Copper 


FIG.  73. 
Electric  Battery  of  Series-connected  Cells. 

zinc  terminal  of  another  cell,  except  that  the  carbon  terminal  of 
the  right-hand  cell  and  the  zinc  terminal  of  the  left-hand  cell 

88 


BATTERY  CONNECTIONS 


89 


are  left  free.     These  two  free  terminals  are  the  terminals  of  the 
battery. 

The  voltage  of  a  series-connected  battery,  measured  between 
its  terminals,  is  equal  to  the  sum  of  the  voltages  of  all  of  the 
cells.  In  this  case  the  battery  voltage  is  four  times  that  of  one 
cell,  since  there  are  four  cells,  all  assumed  to  be  alike.  If  the 
electromotive  force  of  one  cell  is  1.5  volts  on  open  circuit,  then 
the  electromotive  force  of  the  battery  of  four  cells  is  4  X  1.5  =  6 
volts.  If  the  electromotive  force  of  each  cell  drops  to  1.25  volts 
when  the  battery  is  delivering  current  in  regular  service,  then 
the  working  voltage  of  the  battery  is  4X1. 25  =  5  volts. 


FIG.  74. 
Reversed  Cell  in  a  Battery  Intended  to  be  Series-connected. 

The  current  that  the  battery  will  give  is  greater  than  a  single 
cell  will  give.  The  increase  of  current  obtainable  by  connecting 
the  cells  together  is  not  so  great  in  proportion  as  the  increase 
in  the  number  of  cells  in  the  battery.  With  the  four  cells,  it  is 
not  possible  to  get  four  times  as  much  current  as  from  one  cell. 
The  current  will  be  very  nearly  four  times  as  great  with  the  four 
cells,  however,  if  the  resistance  of  the  external  circuit  is  very 
great  in  comparison  with  the  internal  resistance  of  the  battery. 
The  internal  resistance  of  the  series-connected  battery  is  the 
sum  of  the  internal  resistances  of  all  of  the  cells.  If  the  external 
resistance  is  very  low  compared  with  the  internal  resistance  of 
the  battery,  the  series-connected  battery  will  give  only  very 
little  more  current  than  one  cell  alone  will  give. 

77.   Reversed  Cell  in  a  Series  Battery.  —  If  one  of  the  cells  is 


90  ELECTRIC  IGNITION 

wrongly  connected  to  its  neighbors  in  a  series  battery,  so  that 
its  carbon  is  connected  to  the  carbon  of  one  adjacent  cell,  and 
its  zinc  to  the  zinc  of  the  other  adjacent  cell,  the  effect  on  the 
voltage  of  the  battery  is  equivalent  to  removing  two  cells  from 
the  battery.  It  requires  the  electromotive  force  of  one  of  the 
properly  connected  cells  to  counteract  that  of  the  reversed  cell. 
The  current  that  the  battery  will  give  is  less  than  that  of  a 
properly  connected  series  battery  with  two  less  cells. 

Fig.  74  is  a  six-cell  battery  intended  to  be  series-connected, 
but  one  cell  A  is  reversed.  The  battery  is  therefore  somewhat 
less  effective  and  efficient  than  a  properly  connected  four-cell 
series  battery.  While  this  error  of  making  connections  appears 
plain  on  paper,  it  is  one  that  frequently  occurs  and  is  not  so  easy 
to  notice  in  practice. 

Multiple-  or  Parallel-connected  Batteries. 

78.  A  parallel-connected  battery  of  four  cells  whose  positive 
(carbon)  terminals  are  all  connected  together  by  one  wire,  or 
other  conductor,  and  whose  negative  (zinc)  terminals  are  all 
connected  together  by  another  conductor,  is  shown  in  Fig.  75. 


FIG.  75- 
Parallel  or  Multiple  Connection  of  Cells  in  a  Battery. 

Any  place  on  the  wire  connected  to  the  carbons  can  be  taken  as 
the  positive  terminal,  and  any  place  on  the  wire  connected  to  the 
zincs  as  the  negative  terminal. 

The  voltage  of  the  battery  is  the  same  as  that  of  one  cell. 
When  connected  to  an  external  circuit  of  very  high  resistance, 
the  battery  will  deliver  only  slightly  more  than  the  amount  of 
current  in  amperes  that  one  cell  will  deliver  to  the  same  circuit. 
But  when  the  positive  and  negative  wires  of  the  parallel-con- 
nected battery  are  connected  together  by  a  conductor  of  very 


BATTERY   CONNECTIONS 


low  resistance,  such  as  a  thick,  short  copper  rod,  the  four  cells 
will  give  nearly  four  times  as  much  current  as  one  cell  with  its 
terminals  similarly  connected  together. 

In  general,  the  current  is  but  slightly  increased  by  putting 
cells  in  parallel  if  the  resistance  of  the  external  circuit  is  high, 
but  if  the  external  resistance  is  low  compared  with  that  of  the 
battery  the  current  is  materially  increased. 

79.  Reversed  Cell  in  a  Parallel-connected  Battery.  —  In 
Fig.  76  three  cells,  i,  2,  and  3,  are  connected  together.  The 
zinc  of  cell  i  is  connected  to  the  carbons 
of  cells  2  and  3,  and  the  carbon  of  cell  i 
is  connected  to  the  zincs  of  2  and  3. 
When  the  cells  are  connected  together  in 
this  manner,  current  flows  from  the  car- 
bon of  cell  i  to  the  zincs  of  2  and  3,  and 
from  the  carbons  of  cells  2  and  3  to  the 
zinc. of  i.  The  resistances  of  the  circuits 
are  low,  being  only  that  of  the  connecting 
wires  and  of  the  cells.  The  internal  re- 
sistance in  circuit  is  one  and  one-half 
times  that  of  one  cell  when  they  are  connected  in  this  manner. 
Unless  the  connecting  wires  are  very  unusually  thin  and  long, 


FIG.  76. 

Wrong  Connection  of  Cells 
in  a  Battery. 


FIG.  77- 
Reversed  Cell  in  a  Battery  Intended  to  be  Parallel-connected. 

the  total  resistance  of  the  circuit,  internal  plus  external,  is  not 
more  than  that  of  two  cells  added  together.  The  result  is  that 
a  large  amount  of  current  flows  and  the  cells  become  exhausted 
in  a  short  time. 


92  ELECTRIC  IGNITION 

Fig.  77  shows  nine  cells,  eight  of  which  are  connected  in  parallel, 
but  the  remaining  one  A  is  reversed  from  the  position  proper 
for  parallel  connection  with  the  others.  The  result  is  of  the 
same  nature  as  that  just  stated  for  three  cells.  Current  flows 
as  indicated  by  the  arrowheads  on  the  wires.  The  current  is 
not  of  the  same  amount  in  all  parts  of  the  wires,  however.  It 
is  greater  in  the  wires  which  are  between  the  cells  near  A  than 
in  those  between  the  cells  more  remote  from  A.  All  of  the  cells 
will  be  rapidly  exhausted. 

Parallel-series  Batteries. 

80.  Fig.  78  shows  two  sets  of  series-connected  cells  with  four 
cells  in  each  set.  One  set  is  made  up  of  cells  i,  2,  3,  and  4;  the 


FIG.  78. 
Parallel-series  Battery  Connection  of  Two  Sets  of  Series-connected  Cells. 

other  set  is  made  up  of  cells  5,  6,  7,  and  8.  The  two  sets  are 
connected  together  in  multiple,  or  parallel.  Any  point  on  the 
wire  connecting  the  two  carbons  can  be  taken  as  the  positive 
(+)  terminal  of  the  battery,  and  any  point  on  the  wire  connect- 
ing the  two  zincs  can  be  taken  as  the  negative  (— )  terminal. 

The  voltage  of  the  parallel-series  battery  is  the  same  as  that 
of  each  series  of  cells.  In  this  case  the  voltage  is  four  times 
that  of  one  cell,  since  there  are  four  cells  in  each  series. 

More  current  will  be  sent  through  the  external  circuit  by  the 
two  sets  of  series-connected  cells  than  by  one  series  alone.  The 
increase  of  current  will  be  greater  when  the  external  resistance 
is  low  than  when  it  is  high.  It  is  sometimes  convenient  to  con- 
sider each  series  as  a  unit  whose  terminals  are  those  of  the  series. 


BATTERY  CONNECTIONS 


93 


When  this  is  done  the  series  can  be  dealt  with  as  a  single  cell  so 
far  as  regards  its  relations  to  other  units  of  a  similar  nature. 

In  Fig.  79  five  sets,  each  of  four  series-connected  cells,  are 
connected  in  parallel,  or  multiple,  with  each  other.     The  cells 


FIG.  79. 

Parallel  Connection  of  Five  Sets  of  Series-connected  Cells. 


The 


of  each  series  are  in  a  vertical  row  in  the  illustration, 
voltage  of  the  battery  is  four  times  that  of  one  cell. 

81.   Wrong  Arrangement  of  a  Battery.  —  In  Fig.  80  five  series- 
connected  cells  are  shown  in  the  upper  row,  and  four  series- 


FIG.  80. 
Wrong  Arrangement  of  a  Battery. 

connected  cells  in  the  lower  row.  The  two  series  are  connected 
in  parallel  with  each  other.  The  result  is  that  current  flows 
through  the  battery  while  the  external  circuit  is  open,  on 
account  of  the  electromotive  force  of  the  upper  row  of  five  cells 


94 


ELECTRIC  IGNITION 


being  greater  than  that  of  the  lower  row  of  four  cells.  The 
direction  of  the  current  is  indicated  by  the  arrowheads  on  the 
wires.  The  current  will  continue  until  the  electromotive  force 
of  the  five  cells  in  series  drops  to  that  of  the  four  series-connected 
cells.  This  action  means  exhaustion  of  the  five  cells.  A  battery 
should  not  be  made  up  in  this  manner. 

82.  Connection  to  External  Circuit.  —  The  method  of  con- 
necting two  series  batteries  to  the  same  external  circuit  is  shown 
in  Fig.  81.  The  negative  terminal  of  each  series  of  cells  is 
connected  to  one  of  the  contact-points,  or  poles,  of  a  two-point 
switch.  The  contact-points  are  insulated  from  each  other  and 
from  other  parts  of  the  system.  The  positive  terminal  of  each 


FIG.  81. 
Correct  Method  of  Connecting  a  Battery  to  the  External  Circuit. 

set  of  series-connected  cells  is  connected  to  the  external  circuit 
R,  from  which  connection  is  made  to  the  switch-blade.  When 
the  switch-blade  is  in  the  position  shown,  the  upper  row  of  cells 
is  the  only  one  that  delivers  current.  The  other  row  of  cells 
is  on  open  circuit.  If  the  blade  is  moved  into  contact  with  the 
lower  switch-point,  as  indicated  by  the  dotted  lines,  then  the 
lower  row  of  cells  is  brought  into  operation  alone.  By  placing 
the  switch-blade  in  mid-position,  so  that  it  has  contact  with 
both  switch-points,  the  complete  battery  is  cut  into  circuit  and 
it  all  acts  to  furnish  current  to  the  external  circuit.  By  throw- 
ing the  blade  over  so  that  it  has  no  contact  with  either  point, 
the  current  is  completely  cut  off  from  the  external  circuit  and 
there  can  be  no  local  current  in  the  battery  of  the  nature  of  that 
in  Fig.  80,  because  there  is  no  connection  between  the  negative 


BATTERY   CONNECTIONS  95 

terminals  when  the  switch-blade  has  no  contact  with  either  point 
of  the  switch. 

It  may  be  noted  that,  even  when  two  series,  both  of  the  same 
number  of  cells,  are  in  parallel  with  each  other,  and  one  series 
is  run  down  or  exhausted,  while  the  other  is  in  good  condition, 
there  will  be  local  current  in  the  battery  of  the  same  nature  as 
that  in  Fig.  80. 

83.  Screw-top  Battery  Cells.  —  An  exceedingly  convenient 
way  of  connecting  cells  together  in  a  battery  is  by  means  of  a 


FIG.  82. 

Screw-top  Cells  and  Battery  Box.     Stanley  &  Patterson,  23  Murray  Street  and 
27  Warren  Street,  New  York  City. 

screw  top  on  each  cell  and  a  plate  provided  with  suitable  contact 
pieces  and  connections.  Such  cells  and  a  plate  are  shown  in 
Fig.  82.  It  is  only  necessary  to  screw  the  cells  into  the  plate  in 
order  to  make  the  proper  connections.  The  making  of  wrong 
connections,  which  is  not  an  unusual  happening  with  the  ordinary 
cells,  each  having  two  terminal  nuts,  is  thus  entirely  eliminated. 
The  cell  is  connected  into  the  battery  in  a  manner  similar  to 
that  in  which  an  incandescent  electric  lamp  is  connected  into 
the  circuit  of  the  service  wires.  The  carbon  terminal  of  the 
battery  cell  makes  contact  with  a  spring,  and  the  zinc  shell  makes 
contact  with  the  threaded  metallic  ring  into  which  it  screws. 


96 


ELECTRIC  IGNITION 


\ 


The  spring  keeps  the  contacts  pressed  together  and  prevents 
their  jarring  loose. 

The  cells  are  also  made  with  combination  screw-top  and  bind- 
ing-post terminals.     By  means  of  the  latter  the  cells  can  be 

connected  together  with  wires  when 
desired. 

By  the  use  of  "  emergency  spring 
clips  "  the  ordinary  type  of  cell  with 
two  binding  posts  can  be  used  in  the 
4L    A  m      cap  or  plate. 

Fig.  83  shows  five  dry  cells  and  a 
spark-coil  (spark-coils  are  described 
later) ,  each  screwed  into  its  receptacle 
in  the  top-plate  of  the  battery  box. 
The  spark-coil  occupies  practically 
the  same  amount  of  space  as  one  of 
the  cells. 

Battery  boxes  with  this  form  of 
connection  are  also  made  up  with  two 
sets  of  cells  and  a  switch  which,  when  moved  to  its  different 
positions,  connects  the  two  sets  of  cells  either  in  parallel  or  in 
series,  or  connects  either  of  the  sets  into  the  system,  leaving  the 
other  idle. 

The  boxes  are  made  water-tight  for  marine  use  or  for  any 
place  where  there  is  much  water  or  moisture. 


m 

FIG.  83.     (See  also  Fig.  82.) 

Screw-top  Spark-Coil  and  Cells 

in  Battery  Box. 


CHAPTER  X, 

STORAGE  BATTERIES,  ALSO  CALLED  ACCUMULATORS  AND 
SECONDARY  BATTERIES. 

84.  A  storage  battery  is  one  that  must  be  charged  by  passing 
an  electric  current  from  some  exterior  source  through  it  in  order 
to  bring  it  into  a  condition  in  which  it  can  deliver  an  electric 
current.  Before  charging  by  passing  an  electric  current  through 
it,  the  storage  battery  is  inert  and  cannot  deliver  current.  After 
it  has  been  once  charged  and  then  discharged  by  delivering 
current,  it  can  be  recharged  and  will  again  furnish  current  till 
it  is  discharged  a  second  time.  Charging  and  discharging  can 
be  repeated  numerous  times. 

The  charging  current  while  passing  through  the  battery  effects 
chemical  changes  in  the  elements  of  the  battery.  These  chemical 
changes  take  place  in  both  of  the  electrodes  and  in  the  electro- 
lyte. During  discharge  the  reverse  chemical  actions  occur  and 
bring  the  battery  elements  at  least  partly  back  to  their  condi- 
tions before  charging. 

The  name  "  storage  battery  "  is  a  misnomer,  strictly  speaking. 
Electricity  is  not  actually  stored  in  the  battery.  The  charging 
current  passes  through  and  out  of  the  battery,  effecting  chemical 
changes  in  the  elements  of  the  battery  during  its  passage.  The 
distinction  between  this  action  and  the  actual  storage  of  elec- 
tricity will  appear  later  in  connection  with  electric  condensers. 

While  a  great  variety  of  storage  batteries  have  been  constructed 
and  tried  out,  those  in  commercial  use  are  limited  almost  exclu- 
sively to  two  kinds  as  classified  by  the  materials  used  in  them. 
Of  these  two  types,  the  one  which  is  used  by  far  the  more  gener- 
ally is  known  as  a  "  lead  accumulator  "  or  "  lead  storage  bat- 
tery," on  account  of  its  electrodes  being  made  of  the  metal  lead 
and  oxides  of  lead.  The  other  type  is  known  as  the  "  Edison 

97 


98 


ELECTRIC  IGNITION 


storage  battery."     Its  electrodes  are  composed  chiefly  of  nickel 
and  iron. 

85.  The  electrodes,  or  plates,  of  a  lead  storage  cell  are  usually 
made  up  of  plate-shaped  pieces  of  lead,  or  lead  alloy,  which  have 
perforations,  pockets,  or  other  forms  of  receptacles  filled  with 
the  electrically  active  material.  This  active  material  is  usually 
put  into  the  pockets  in  the  form  of  paste  during  the  construction 
of  the  cell.  It  is  composed  chiefly,  when  first  put  in,  of  an 


FIG.  84. 
Electrode,  Plate,  or  Grid  of  a  Lead  Storage  Battery. 

oxide,  or  oxides,  of  lead.  The  plates  are  then  treated  chemically 
and  electrically  so  as  to  cause  the  paste  to  set  firm  and  hard,  and 
to  change  its  chemical  composition.  The  plate,  or  plates,  to 
form  the  electrode  to  which  the  positive  terminal  of  the  cell  is 
connected  are  treated  so  that  the  final  condition  of  the  paste  is 
dioxide  of  lead  (PbC^),  and  the  plate  has  a  brown  color,  including 
the  paste.  The  plate,  or  plates,  to  form  the  other  electrode  are 
treated  so  as  to  remove  the  oxygen  from  the  compound  and  leave 
metallic  lead  in  a  porous,  or  spongy,  condition  with  the  charac- 
teristic color  of  metallic  lead. 


STORAGE  OR   SECONDARY  BATTERIES 


99 


One  form  of  lead  grid  for  a  storage  battery  is  shown  in  Fig.  84. 
It  has  rectangular  perforations  for  receiving  and  holding  the 
paste.  The  lug  projecting  upward  is  for  making  connection  to 
other  plates  or  to  the  external  circuit. 

86.  Complete  Storage  Cell.  —  Fig.  85  shows  several  complete 
plates  grouped  together  to  form  the  electrodes  of  one  cell.  Three 


FIG.  85. 
Group  of  Plates  for  a  Lead  Storage  Cell. 

of  the  plates  are  fastened  together  by  a  bar,  or  strap,  which 
carries  one  of  the  terminals  of  the  cell  at  the  top.  The  other 
two  plates  are  fastened  together  in  a  similar  manner  and  have 
the  other  terminal  of  the  cell  at  the  top.  The  pockets  of  the 
plates,  or  grids,  are  shown  filled  with  paste. 

Separators  are  used  between  the  plates  to  keep  them  from 
coming  into  contact  with  each  other.     One  of  the  separators 


IOO 


ELECTRIC  IGNITION 


FIG.  86. 
Separator  for  Placing  between  the  Plates  of  a  Storage  Cell. 


FIG.  87. 

Storage  Cell  Containing  the  Parts  shown  in  Figs.  84,  85,  86  and  88. 
Dayton  Electrical  Manufacturing  Company,  Dayton,  Ohio. 


STORAGE  OR   SECONDARY  BATTERIES  IOI 

used  with  these  particular  plates  is  shown  in  Fig.  86.  It  is  made 
of  hard  rubber  in  one  piece  and  has  the  general  form  of  a  number 
of  bars  laid  across  each  other  at  right  angles. 

The  complete  cell  is  made  up  of  the  plates  and  separators 
immersed  in  an  electrolyte  of  dilute  acid  solution  contained  in  a 
jar.  The  electrolyte  should  completely  cover  the  main  portion 
of  the  plates,  but  the  terminals  and  upper  portion  of  the  lugs 
extend  above  the  liquid. 

The  electrolyte  is  generally  dilute  sulphuric  acid.  The  water 
used  with  the  acid  should  be  very  pure,  as  distilled  water. 

A  complete  storage  cell  having  plates  and  separators  like 
those  just  described  is  shown  in  Fig.  87.  The  jar  is  of  hard 
rubber  suitable  for  portable  work.  It  is  provided  with  a  cover 
which  is  sealed  on  to  make  the  cell  tight,  except  a  small  opening, 
or  vent,  which  is  shown  between  the  terminals. 

The  cover  of  the  cell  is  shown  in  section  in  Fig.  88.  The  vent 
is  so  made  that  the  bubbles  of  gas,  escaping  during  the  charging 


FIG.  88. 
,   Cover  of  Cell  shown  in  Fig.  87. 

of  the  cell  and  carrying  the  .liquid  electrolyte  up  with  them,  can 
escape  through  the  upper  part  of  the  vent-plug  without  carrying 
the  liquid  outside  of  the  cell.  The  conical  terminal  of  one  set 
of  plates  is  shown  in  the  opening  through  the  left-hand  end  of 
the  cover.  This  cone  is  surrounded  by  a  rubber  washer  and  is 
drawn  up  tight  so  as  to  make  a  liquid-proof  joint. 

87.  The  voltage  of  a  storage  cell  having  lead  plates  and  dilute 
sulphuric  acid  electrolyte  is  about  2.2  volts  on  open  circuit.  It 
drops  below  the  open-circuit  value  as  soon  as  the  external  cir- 
cuit is  closed  and  current  flows.  The  pressure  drop  is  approxi- 


102  ELECTRIC  IGNITION 

mately  proportional  to  the  amount  of  current  flowing,  for  a 
given  cell,  when  the  cell  is  in  good  condition.  The  pressure 
decreases  very  slowly  during  discharge  until  the  battery  is  almost 
completely  discharged,  and  then  begins  to  drop  very  rapidly  as 
the  discharge  continues. 

The  voltage  is  independent  of  the  number  of  plates  in  the  cell. 
It  is  the  same  when  there  is  only  one  positive  plate  and  one 
negative  plate,  as  when  there  are  several  of  each.  In  one  cell 
the  plates  are  generally  all  immersed  in  the  same  lot  of  electro- 
lyte contained  in  one  jar  with  no  partitions  to  separate  one 
portion  of  the  liquid  from  another.  Exceptions  to  the  last  state- 
ment are  some  unusual  types  of  cells  with  porous  jars. 

88.  The  maximum  rate  of  discharge  of  a  storage  cell,  without 
injury  to  the  cell,  is  approximately  proportional  to  the  amount 
of  surface  area  of  active  material  of  the  electrodes  in  contact 
with  the  liquid  electrolyte.     If  the  same  size  and  make  of  plates 
are  used  to  make  up  cells  having  different  numbers  of  plates  in 
them,  then  the  safe  maximum  amperage  of  the  cells  will  be 
approximately  proportional  to  the  number  of  plates  in  them. 
The  maximum  safe  rate  of  discharge  of  a  cell  having  15  plates 
is  about  three  times  as  great  as  that  of  one  having  only  5  plates, 
the  plates  in  both  being  of  the  same  size  and  make,  as  already 
stated.     The  rate  of   discharge  is  measured  in  amperes.     An 
excessive  rate  of  discharge  is  injurious  to  the  cell.    It  causes  the 
paste  to  swell  and  even  to  drop  from  the  grids. 

89.  A  storage  battery  is  composed  of  storage  cells  connected 
together.     Any  of  the  methods  of  connection  that  have  been 
given  for  primary  cells  can  be  used  for  storage  cells. 

The  storage  batteries  used  for  ignition  purposes  are  generally 
made  up  of  two  or  three  cells  connected  together  and  inclosed  in 
a  case.  A  battery  of  this  nature  does  not  differ  much,  in  appear- 
ance from  a  single  cell. 

The  plates  of  three  storage  cells  are  shown  connected  together 
in  series  in  Fig.  89.  The  two  positive  plates  of  the  right-hand 
set  are  Connected  by  a  lead  strap  to  the  three  negative  plates 
of  the  middle  set.  The  two  positive  plates  of  the  middle  set 
are  similarly  connected  to  the  three  negative  plates  of  the  left- 


STORAGE  OR  SECONDARY  BATTERIES 


103 


FIG.  89. 
Connected  Plates  of  a  Three-cell  Storage  Battery. 


FIG.  90. 
Three-cell  Storage  Battery  with  Cover  Removed. 


104  ELECTRIC  IGNITION 

hand  set.    The  two  threaded  bolts  at  the  opposite  corners  of 
the  entire  group  are  the  terminals  of  the  battery. 

In  Fig.  90  a  case  containing  the  three  sets  of  plates  and  their 
corresponding  jars  is  shown  before  the  sealing  compound  is  put 
on  the  top.  The  complete  battery  is  shown  in  Fig.  91.  The 


FIG.  91. 
Complete  Three-cell  Storage  Battery  containing  Plates  shown  in  Fig.  89. 

knurled  nuts  on  the  terminals  are  shown  just  above  the  marks 
"P+"  and  "  N-." 

The  voltage  of  the  three  cells  connected  in  series  is  three  times 
that  of  one  cell  alone.  While  the  three  cells  will  send  more 
amperes  of  current  through  a  given  external  resistance  than  one 
cell  will,  the  maximum  allowable  amperage  is  the  same  for  the 
three  cells  as  for  one  cell  alone. 

90.  "  Exide  "  Storage  Battery.  —  Fig.  92  shows  another  form 
of  battery  that  used  lead  plates  and  dilute  sulphuric  acid  electro- 
lyte. It  is  commercially  known  as  the  "  Exide  "  battery.  One 
side  of  both  the  case  and  the  jar  is  removed  in  the  illustration, 


STORAGE  OR   SECONDARY  BATTERIES  105 

H 


Exide  Storage  Battery. 

A.  Terminals  of  battery. 

B.  Inverted  petticoat. 

C.  Pillar  post. 

D.  Plate  strap. 

E.  Lug  on  plate. 

F.  Positive  plate. 

G.  Acid-resisting  paint. 
H.   Handle. 

I.     Vent  plugs. 

J.     Plastic  asphaltum. 

K.  Beveled  edge  at  top  of  wood  case. 


FIG.  92. 

Electric  Storage  Battery  Company,  Philadelphia,  Pa. 
L.    Connector. 
M.   Hard  rubber  cover,  sealed  in  with 

asphaltum  J. 

N.    Apron.     Part  of  plate  strap. 
O.    Negative  plate. 
P.     Wooden  separator. 
Q.    Acid-resisting  compound. 
R.    Hard  rubber  cell  or  jar. 
S.     Hard  rubber  ribs. 
T.    Expansion  joint. 


106  ELECTRIC   IGNITION 

and  some  of  the  interior  members  partly  broken  away  to  show 
the  construction. 

'The  separator  between  adjacent  positive  and  negative  plates 
is  made  of  wood  chemically  treated  before  using.  The  chemical 
treatment  of  the  wood  is  to  remove  any  substance  that  might  be 
deleterious  to  the  cell.  There  are  deep  vertical  grooves  in  the 
separator  on  the  side  that  goes  next  to  the  positive  plate.  These 
grooves  are  to  allow  free  circulation  of  the  electrolyte  and  escape 
of  gas  while  the  cell  is  being  charged.  In  some  forms  of  this 
battery  a  thin  sheet  of  hard  rubber  with  numerous  perforations 
is  placed  between  the  positive  plate  and  the  grooved  side  of  the 
separator.  The  plates  rest  on  high  rubber  ribs  at  the  bottom 
of  the  jar,  so  that  there  is  ample  space  left  for  the  sediment  which 
collects  at  the  bottom  of  the  jar.  This  is  important,  since  the 
battery  is  short-circuited  internally  if  the  sediment  rises  high 
enough  to  touch  the  electrodes.  An  apron  N  on  each  strap 
which  connects  the  plates  prevents  the  wooden  separators  from 
rising  on  account  of  the  buoyant  action  of  the  liquid.  Each 
vent  plug  /  is  a  hollow  cone  with  a  hole  near  the  top  to  allow 
the  escape  of  gas  from  the  cell  while  it  is  being  charged,  and  a 
drainage  hole  at  the  bottom  through  the  apex  of  the  cone  to  let 
the  electrolyte  flow  back  into  the  cell,  in  case  any  of  the  liquid 
is  carried  up  with  the  escaping  gas. 

The  binding  posts  are  formed  so  as  to  prevent  the  acid  electro- 
lyte from  creeping  up  and  spreading  over  the  top  of  the  cell. 
This  prevention  is  accomplished  by  forming  the  lead  alloy  into 
the  shape  of  an  "  inverted  petticoat  "  which  is  below  the  binding 
screw  far  enough  to  be  covered  with  the  sealing  compound  of 
"  plastic  asphaltum  "  that  covers  the  top  of  the  battery  except 
the  terminals  and  vents.  The  edges  of  the  wood  case  are  beveled 
at  the  top  so  that  the  sealing  compound  covers  them  and  thus 
prevents  the  acid  from  soaking  down  into  the  wood  if  any  of 
the  electrolyte  is  spilled  over  the  top.  The  acid  is  injurious  to 
the  wood. 

Each  grid  is  cast  in  one  piece  and  has  the  form  of  numerous 
small  horizontal  bars  held  in  place  by  several  thin  vertical  strips. 
A  part  section  of  the  grid,  made  by  cutting  the  plate  in  two 


STORAGE  OR   SECONDARY  BATTERIES 


107 


between  two  of  the  vertical  strips,  is  shown  in  Fig.  93,  in  which 
A  is  a  side  view  of  part  of  one  of  the  vertical  strips.  The  small 
horizontal  bars  are  shown  in  cross-section  at  A,  B,  C,  D,  E, 
and  F.  There  are  of  course  a  great  many  more  horizontal  bars 
in  the  entire  grid  than  shown  in  this  section.  The  exposed  sur- 
face of  each  horizontal  bar  appears  as  a  line,  as  shown  in  the 
preceding  figure.  The  object  of  making  the  grid  in  this  form  is 


FIG.  93. 

Section  of  Grid  for  Battery 
shown  in  Fig.  92. 


FIG.  94. 

Phantom  View  of  Exide 
Storage  Battery. 


to  expose  as  great  a  surface  of  the  paste  to  the  electrolyte  as 
possible,  and  at  the  same  time  provide  a  light-weight  grid  which 
holds  the  paste  securely  in  place. 

A  phantom  view  of  an  Exide  battery  intended  for  ignition 
usage  is  shown  in  Fig.  94.  This  battery  is  of  a  slightly  earlier 
form  than  that  shown  in  Fig.  92,  but  is  the  same  in  a  general  way, 
lacking  only  some  of  the  improvements  in  detail  that  appear  in 
the  latter  form.  The  battery,  Fig.  94,  is  made  up  of  three  cells 
connected  in  series.  Each  of  the  three  cells  has  three  positive 
plates  and  four  negative  ones.  Each  cell  is  provided  with  its 
own  vent  plug. 

91.  Charging  the  Storage  Battery.  —  A  storage  battery  of  the 
ignition  type  is  generally  charged  and  ready  for  use  when  sent 


108  ELECTRIC  IGNITION 

out  from  the  factory.  After  it  has  been  discharged  it  can  be 
charged  again  by  connecting  to  some  exterior  direct-current 
source  of  electric  supply  and  sending  current  through  it  in  the 
reverse  direction  from  that  in  which  it  discharges.  The  positive 
side  of  the  source  of  supply  must  be  connected  to  the  positive 
terminal  of  the  storage  battery,  and  the  negative  of  the  supply 
to  the  negative  of  the  battery.  An  alternating  current  cannot 
be  used  directly  for  charging  a  storage  battery,  but  it  can  be 
rectified  by  suitable  apparatus  for  transforming  it  into  a  direct 
current  which  can  be  sent  through  the  battery  to  charge  it. 

In  charging  the  battery,  as  in  discharging  it,  the  amount  of 
current  must  be  kept  within  the  maximum  safe  amperage  of  the 
battery.  This  is  ordinarily  accomplished  by  the  use  of  suitable 
regulating  apparatus  inserted  in  the  supply  circuit.  A  rheostat 
is  generally  used  for  regulating  the  amount  of  current. 

Gas  is  formed  in  the  battery  while  charging  it,  slowly  at  first, 
and  then  more  rapidly.  The  formation  of  gas  is  especially  rapid 
when  the  battery  has  become  almost  completely  charged.  (See 
also  Chapter  XXVI.) 

92.  Chemical  Action  in  a  Lead  Storage  Battery.  —  When  a 
storage  cell  is  in  a  fully  charged  condition  and  ready  for  use, 
the  active  material  in  the  plates  connected  to  the  positive  ter- 
minal is  in  the  chemical  form  of  dioxide  of  lead  (PbO2)  and  has 
a  brown  color.  In  the  negative  plates  the  active  material  is  in 
the  form  of  porous,  or  spongy,  metallic  lead  and  has  a  gray  color. 
Although  this  has  been  stated  before,  it  is  repeated  here  to  bring 
it  fresh  in  mind. 

During  the  discharge  of  the  cell,  the  dioxide  of  lead  in  the  posi- 
tive plate  is  partly  changed  to  monoxide  of  lead  (PbO)  by  the  loss 
of  part  of  its  oxygen.  The  metallic  lead  in  the  negative  plate  is 
partly  changed  into  monoxide  of  lead  (PbO)  also,  by  the  addition 
of  oxygen  to  it.  The  amount  of  sulphuric  acid  in  the  electrolyte 
is  reduced  by  decomposition  into  sulphur  and  water,  so  that  the 
electrolyte  becomes  weaker  and  has  a  lower  specific  gravity. 

During  the  charging  of  the  cell  the  above  reactions  are  reversed 
and  the  elements  of  the  cell  are  restored,  more  or  less  completely, 
to  their  first-mentioned  condition  of  the  charged  cell. 


STORAGE  OR   SECONDARY  BATTERIES 


109 


93.  The  capacity  of  a  storage  cell  is  measured  in  ampere-hours. 
An  ampere  of  current  flowing  for  one  hour  is  an  ampere-hour. 
So  is  half  an  ampere  flowing  for  two  hours,  or  four  amperes  flow- 
ing for  a  quarter  of  an  hour,  etc.  Four  amperes  flowing  for  one 
hour  are  four  ampere-hours,  and  the  same  amount,  four  amperes, 
flowing  for  two  hours  are  eight  ampere-hours.  In  general,  the 
current  in  amperes,  multiplied  by  the  number  of  hours  during 
which  it  flows,  equals  the  number  of  ampere-hours. 

Amperes  of  current  X  hours  of  time  =  ampere-hours. 

In  order  to  fully  specify  a  storage  battery,  its  voltage,  or  the 
number  of  cells  in  it,  must  be  stated  in  connection  with  its  capac- 
ity in  ampere-hours.  The  following  table  refers  to  lead  storage 
batteries  for  ignition  use,  as  made  by  one  manufacturer. 

SIZE   AND   CAPACITY   OF   IGNITION   STORAGE  BATTERIES. 

All  of  these  batteries  are  9  inches  high  and  6f  inches  wide  over  all. 


Number  of 
Cells  in  Battery. 

Volts  Pressure. 
(Approximate.  ) 

Ampere-hours 
Capacity  at  Ser- 
vice Rate. 

Length  over  All. 

Weight. 

Inches. 

Pounds. 

I 

2 

"I                      f 

3i 

8| 

2 

4 

i                     J 

5ii 

I7 

3 

6 

7^ 

25! 

4 

8 

I 

9& 

34 

i 

2 

i          r 

4tt 

12 

2 

4 

60    J 

7& 

24 

3 

6 

f         1 

9rl 

351 

4 

8 

J          I 

W* 

47^ 

i 

2 

1          r 

5if 

151 

2 

3 

4 
6 

80 

lift 

3°t 
46 

4 

8 

J                  I 

?sA 

61 

i 

2 

1          r 

6^| 

19 

2 

3 

4 
6 

100 

i4fl 

37^ 
55^ 

4 

8 

J          I 

I9T* 

74 

CHAPTER  XI. 


FLOATING  THE   STORAGE  BATTERY  ON  THE  LINE   OF  A 
DIRECT-CURRENT   GENERATOR. 

94.  A  storage  battery  can  be  kept  in  continuous  service  by 
the  method  of  operating  known  as  "  floating  the  battery  on  the 
line."  A  direct-current  generator  which  will  give  a  voltage 
somewhat  higher  than  that  of  the  battery  is  ordinarily  used, 
but  modified  forms  of  the  system  use  generators  giving  a  pressure 
very  much  higher  than  that  of  the  battery,  sometimes  several 
times  that  of  the  battery. 

It  is  assumed  in  the  following  discussion  that  the  generator 
maintains  a  constant,  or  nearly  constant,  voltage  slightly  higher 
than  that  of  the  storage  battery  on  open  circuit  when  fully 
charged. 

One  arrangement  of  the  apparatus  for  the  above  method  of 
operation  is  shown  diagrammatically  in  Fig.  95,  in  which  A 


FIG.  95. 
Direct-current  Generator  and  a  Battery  Floated  on  the  Line,  with  a  Light  Load. 

represents  the  commutator  and  brushes  of  a  direct-current  gen- 
erator which  maintains  a  constant  voltage,  or  nearly  so;  B  is 
the  storage  battery,  and  C  is  any  piece  of  electrical  apparatus, 
such  as  an  incandescent  lamp,  through  which  current  is  sent. 
The  current  flows  from  the  positive  (+)  brush  of  the  generator 
to  the  junction  D,  where  it  divides,  part  flowing  through  the 

no 


FLOATING  THE  STORAGE  BATTERY 


III 


lamp  C  and  the  remainder  through  the  storage  battery  B  in  the 
direction  to  charge  it.  These  two  currents  come  together  again 
at  the  junction  E  and  flow  through  the  same  wire  to  the  negative 
(— )  brush  of  the  generator  A.  The  direction  of  the  current  is 
indicated  by  the  arrowheads  on  the  lines  representing  the  cir- 
cuits. This  action  continues  as  long  as  the  conditions  remain 
unchanged. 

Now  suppose  that  several  additional  lamps  are  added  to  the 
circuit,  as  shown  in  Fig.  96,  which  are  the  maximum  number 
that  the  system  is  intended  to  operate.  The  battery  now  dis- 


~l 


FIG.  96. 
Battery  Floated  on  the  Line,  with  Heavy  Load. 

charges  so  as  to  furnish  current  to  the  lamps,  thus  aiding  the 
generator  which  still  supplies  current,  all  of  which  flows  through 
the  lamps.  The  battery  and  generator  now  operate  in  conjunc- 
tion, both  sending  current  through  the  lamps.  The  generator 
delivers  more  current  when  all  of  the  lamps  are  in  the  circuit 
than  when  only  one  is  in  the  circuit.  If  all  of  the  six  lamps  are 
alike,  they  will  take  about  six  times  as  much  current  as  any  one 
of  them  alone. 

The  greater  number  of  lamps  requiring  more  current  than  one, 
lowers  the  voltage  at  the  lamps  and  also  the  difference  of  pressure 
at  the  junction  points  D  and  E.  When  the  difference  of  pressure 
between  D  and  E  drops  to  a  lower  value  than  the  voltage  of  the 
storage  battery  on  open  circuit,  the  battery  begins  to  deliver 
current  instead  of  receiving  it,  as  in  the  case  where  only  one 
lamp  was  in  circuit.  The  lowering  of  the  pressure  between  D 
and  £,  due  to  increasing  the  number  of  lamps,  causes  the  genera- 
tor to  deliver  more  current. 


112 


ELECTRIC  IGNITION 


Another  method  of  arranging  the  apparatus  is  shown  in  Fig.  97 
for  one  lamp,  and  in  Fig.  98  for  several  lamps.  The  operation 
of  this  system  is  in  a  general  way  the  same  as  that  of  the  preced- 
ing two  figures.  The  direction  of  current  is  indicated  by  the 
arrowheads  on  the  circuits. 

If  the  circuit  is  broken  between  the  generator  and  other 
apparatus,  the  generator  will  of  course  become  inoperative  so 


FIG.  97. 
Modified  Form  of  Fig.  95. 


FIG.  98. 
Modification  of  Fig.  96. 

far  as  the  other  parts  of  the  system  are  concerned.  The  battery 
will  then  furnish  all  of  the  current  required  for  the  lights.  This 
within  the  limits  of  the  battery. 

Still  another  method  of  arrangement  is  shown  in  Fig.  99.  The 
dynamo  A  is  placed  between  the  storage  battery  B  and  the  load 
C.  When  the  load  is  small,  as  represented  by  one  lamp  C,  and 
the  generator  is  at  its  proper  voltage,  it  sends  current  through 
both  the  storage  battery  to  charge  it  and  through  the  lamp.  The 
current  from  the  generator  divides  at  D,  part  going  to  the  lamp 
and  part  to  the  positive  side  of  the  storage  battery,  as  indicated 


FLOATING  THE   STORAGE  BATTERY  113 

by  the  arrowheads.  These  divided  currents  unite  again  at  E 
and  flow  together  to  the  negative  brush  of  the  generator.  If  the 
full  load  is  put  on,  as  represented  by  several  lamps  in  Fig.  100, 
then  the  storage  battery  discharges  into  the  circuit,  thus  aiding 
the  generator.  Both  send  current  through  the  lamps.  The 
direction  of  the  current  is  indicated  by  the  arrowheads.  The 
two  currents  unite  at  D  and  flow  together  through  the  lamps. 


FIG.  99. 

Electric  Generator  between  the  Load  and  the  Battery  which  is  Floated  on  the 

Line.     Light  Load. 


m 

I                       r4 

.7*N                             -PF* 

® 


®c 


FIG.  100. 

Electric  Generator  between  Heavy  Load  and  a  Battery,  which  is  Floated  on  the 

Line. 

They  then  separate  at  E,  part  going  to  the  negative  brush  of 
the  generator  and  the  remainder  to  the  negative  side  of  the 
battery. 

95.  An  automatic  cut-out  is  used  on  some  storage-battery  and 
generator  systems  in  which  the  storage  battery  is  floated  on  the 
line.  This  has  been  mentioned  in  connections  with  Figs.  63 
and  64.  The  purpose  of  this  cut-out  is  to  prevent  the  flow  of  a 
large  reverse  current  from  the  battery  through  the  generator  in 
case  the  latter  slows  down  so  as  not  to  give  a  sufficiently  high 
voltage,  or  in  case  of  its  complete  stoppage.  It  is  often  desirable, 


ELECTRIC  IGNITION 


and  especially  so  for  ignition  service  where  the  motor  runs  inter- 
mittently, to  have  the  cut-out  also  operate  automatically  to  put 
the  generator  into  circuit  when  its  speed  is  again  sufficient  to 
give  the  necessary  voltage. 

An  electric  system  with  an  automatic  cut-out  of  the  last- 
mentioned  type  is  shown  diagrammatically  in  Fig.  101.  The 
cut-out  consists  of  an  electromagnet  with  a  double  winding  and 
an  armature  with  a  contact-point  at  one  end.  The  cut-out 
armature  as  shown  consists  of  a  blade  spring  to  which  is  fastened 
a  contact  point  and  a  soft  steel  disk,  the  latter  opposite  the  end 
of  the  magnet  core.  One  end  of  the  blade  spring  is  fastened  to  a 


•DTG7Generator> 


la  C 

•  [ 

' 

D 

At 
C 

Core--: 
Shunt  —^ 
Coil 

Seriesx^ 
Coil       ^ 

itomatic 
ut-Out 

11 

Storage 
Battery 

9~ 

~*  

^T^ 

k  '     F 

_^  —  f 

b 

E 

i 

^kcot 

^-kfJ     tArmatuie          Po 

FIG.  101. 
Complete  Dynamo  and  Storage-battery  System  with  an  Automatic  Cut-Out. 

stationary  block  G  in  such  a  way  that  the  elastic  action  of  the 
spring  tends  to  draw  the  armature  away  from  the  core  and  sepa- 
rate the  contact-points.  When  the  core  is  magnetized  it  attracts 
the  cut-out  armature  and  holds  it  in  the  position  shown  with  its 
contact-point  pressed  against  the  mating  contact-point  to  which 
is  connected  one  end  of  one  of  the  magnetizing  coils  of  the  cut-out. 
If  the  magnetism  of  the  cut-out  core  becomes  weak,  the  armature 
then  springs  away  from  it  so  as  to  separate  the  contact-points. 
One  coil  of  the  cut-out  is  permanently  connected  in  series  with 
the  field-magnet  coils  of  the  shunt-wound  generator.  This  coil, 
marked  "  shunt-coil "  in  the  figure,  has  a  comparatively  great 
number  of  turns  of  insulated  wire  large  enough  to  continuously 
carry  the  current  that  flows  through  the  field-coils  of  the  genera- 
tor. The  other  coil  of  the  cut-out,  marked  "  series-coil,"  is  in 
series  with  the  main  circuit  of  the  generator.  This  coil  has  com- 


FLOATING  THE   STORAGE  BATTERY  115 

paratively  few  turns  of  insulated  wire  large  enough  to  carry  all 
of  the  current  from  the  generator. 

When  the  system  is  operating  in  the  regular  manner,  the  cur- 
rent flows  through  the  circuits  in  the  direction  indicated  by  the 
arrowheads  on  the  lines  representing  the  circuits.  Since  the 
direction  of  flow  in  the  two  lines  leading  from  the  storage  battery 
to  the  points  D  and  E  may  be  first  in  one  direction  and  then  in 
the  other,  it  is  indicated  by  a  pair  of  opposed  arrowheads  on 
each  line.  The  currents  in  both  coils  of  the  cut-out  flow  in  the 
same  direction  around  the  core,  and  both  magnetize  the  core  in 
the  same  direction  so  as  to  keep  the  contact-point  of  the  cut-out 
armature  drawn  up  against  its  mate. 

If  the  generator  slows  down  so  that  its  voltage  drops  below 
that  of  the  battery,  then  the  battery  sends  current  back  to  the 
generator  and  through  it  and  the  cut-out  coils.  This  back  cur- 
rent flows  from  the  positive  (+)  terminal  of  the  battery  to  D 
and  then  to  the  positive  (+)  brush  of  the  generator,  where  it 
divides,  part  flowing  through  the  field-coils  of  the  generator  and 
the  shunt-coil  of  the  cut-out  in  the  same  direction  as  before  to 
the  junction  F.  The  remainder  of  the  back  current  flows  through 
the  armature  of  the  generator  to  the  negative  (— )  brush  and 
thence  to  F.  From  F  all  of  the  back  current  flows  through  the 
series-coil  of  the  cut-out  in  the  opposite  direction  from  that 
in  which  it  flowed  before.  The  direction  of  the  back  current 
through  the  main  circuit  is  indicated  by  the  arrows  alongside  the 
circuit. 

The  back  current  through  the  series-coil  of  the  cut-out  opposes 
the  magnetizing  action  of  the  current  in  the  shunt-coil  and  demag- 
netizes the  core  of  the  cut-out  enough  to  allow  the  cut-out  arma- 
ture to  spring  back  so  as  to  separate  the  contact-points.  The 
current  through  the  series-coil  stops  as  soon  as  the  circuit  is 
opened  by  the  separation  of  the  contact-points.  A  weak  current 
continues  in  the  shunt-coil  as  long  as  the  generator  keeps  running 
at  slow  speed.  This  cur  rent  xeases  as  soon  as  the  generator  stops 
running.  There  is  then  no  current  in  any  part  of  the  system  to  the 
right  of  the  points  D  and  E.  The  battery  keeps  sending  current 
continuously  through  the  part  of  the  system  to  the  left  of  it. 


n6 


ELECTRIC  IGNITION 


If  the  generator  is  started  again,  the  contact-points  of  the 
cut-out  still  remaining  apart,  it  will  at  first  send  current  through 
only  its  field-coils  and  the  shunt-coil  of  the  cut-out,  including 
of  course  the  generator  armature  and  the  connections  of  this 
circuit.  When  the  voltage  at  the  brushes  of  the  generator  be- 
comes somewhat  higher  than  that  of  the  battery  as  the  speed 
increases,  the  current  sent  through  the  shunt-coil  is  great  enough 
to  magnetize  the  core  sufficiently  to  draw  the  cut-out  armature 
toward  it  and  thus  close  the  circuit  at  the  contact-points.  This 
establishes  the  normal  condition  of  operation. 

The  size  of  the  cut-out  as  shown  in  the  figure  is  much  larger 
in  proportion  to  the  other  apparatus  than  it  is  in  the  constructed 
apparatus.  It  is  shown  large  in  order  to  make  its  construction 
appear  plainly. 

A  compound-wound  direct-current  generator  can  also  be  used 
with  a  cut-out  of  this  nature. 

In  Fig.  102  a  storage  battery  is  floated  on  the  line  of  a  variable- 
speed  direct-current  dynamo.  A  volt-ammeter  is  included  in 


VOLT  AMMETER 


U=-11CONNECT(-1)AND(+4) 

WIRES  THROUGH  PROPER 
SWITCHES  FOR  IGNITION 
AND  LIGHTING  THE  SAME. 

^4JAS  FROM  A  BATTERY 


APLCO  10* 

PATENTS  DYNAMO  WITH  LOAD 

APLCO  LIGHTING  STORAGE  BATTERY  PENDING  REGULATOR  &  CUT-OUT 

FIG.  102. 

APLCO  Electric  System  with  Battery  Floated  on  the  Line.     Apple  Electric 
Company,  Dayton,  Ohio. 

the  system,  for  measuring  the  voltage  of  the  battery  and  the 
amount  of  current  flowing  through  the  battery. 

The  hand,  or  pointer,  of  the  volt-ammeter  is  shown  pointing 
to  the  zero  of  the  scales  on  the  dial.     When  the  dynamo  is  send- 


FLOATING  THE   STORAGE  BATTERY 


117 


ing  current  through  the  storage  battery  to  charge  it,  the  indicator 
hand  moves  to  the  left  and  points  to  the  lower  scale,  which  gives 
the  reading  of  the  amount  of  charging  current.  When  the 
battery  is  discharging,  the  indicator  hand  moves  to  the  right  of 
the  zero  and  indicates  the  current  rate  of  discharge.  To  obtain 
the  voltage  of  the  battery,  the  push-button  ("  press-button  ") 
must  be  pressed  in.  The  indicator  hand  then  points  to  the 
pressure  on  the  upper  scale.  The  current  through  the  battery 
is  indicated  continuously  except  during  the  time  the  button  is 
pressed  in  to  obtain  the  reading  of  the  voltage. 

The  dynamo  is  provided  with  an  automatic  cut-out  and  a  load 
regulator.  The  latter  regulates  the  current  delivered  by  the 
dynamo  within  a  limited  range.  It  does  this  by  automatically 
varying  the  resistance  in  the  field-coil  circuit.  The  load  regu- 
lator makes  it  possible  to  drive  the  armature  of  the  dynamo  at 
a  rotative  speed  proportional  to  that  of  the  crank-shaft  of  the 
motor,  even  when  the  speed  of  the  crank-shaft  is  extremely 
variable,  as  in  automobile  and  boat  motors,  and  still  keep  the 
current  from  the  generator  approximately  constant  as  long  as 
the  armature  rotates  fast  enough  to  generate  sufficient  voltage. 
The  automatic  cut-out  opens  the  dynamo  circuit  when  the  speed 
of  the  armature  falls  below  the  requisite  amount. 


FIG.  103. 
Two-voltage  System  with  Two  Storage  Batteries  Floated  on  the  Line. 

96.  A  two-voltage  system  with  two  storage  batteries  floated 
on  the  line  is  shown  in  Fig.  103.  Two  storage  batteries  of  the 
same  voltage  are  connected  in  series  between  the  positive  and 
negative  sides  of  the  circuit  in  the  same  manner  as  the  one 


Il8  ELECTRIC  IGNITION 

storage  battery  in  Figs.  99  and  100.  This  system  gives  two 
voltages,  one  double  the  other  when  the  two  storage  batteries 
are  of  the  same  voltage,  as  stated. 

A  two-point  switch  in  the  ignition  circuit  can  be  closed  on 
either  of  the  two  contact-points  by  placing  the  pivoted  arm  in 
the  corresponding  position. 

The  flow  of  current  through  the  system  depends  on  the  amount 
of  electrical  resistance  of  the  ignition  apparatus  relative  to  the 
voltage  of  the  storage  batteries.  The  resistance  of  the  ignition 
apparatus  is  ordinarily  low  enough  for  the  method  of  operation 
to  be  as  follows: 

When  the  voltage  of  the  dynamo  brushes  is  higher  than  that 
of  the  storage  batteries  in  series,  as  measured  between  the  points 
T  and  U,  and  the  switch  is  closed  as  shown,  then  while  the  cir- 
cuit is  closed  in  the  ignition  apparatus,  the  current  from  the 
positive  brush  of  the  dynamo  flows  to  O,  then  through  the  switch 
and  ignition  apparatus  to  S,  thence  through  battery  2  and  to  the 
negative  brush  of  the  dynamo.  At  the  same  time  current  flows 
from  the  positive  terminal  T  of  battery  i  to  0,  then  through  the 
switch  and  ignition  apparatus  to  S,  and  thence  to  the  negative 
terminal  of  battery  i.  While  the  circuit  is  broken  in  the  igni- 
tion apparatus  in  the  usual  manner  of  operation,  the  dynamo 
sends  all  of  its  current  to  T  and  through  both  storage  batteries 
in  series  so  as  to  charge  them.  If  the  dynamo  stops  and  is  cut 
out  of  circuit,  then  battery  i  supplies  the  current  to  the  ignition 
apparatus,  and  battery  2  is  idle. 

When  the  switch  is  closed  as  shown,  and  the  voltage  at  the 
dynamo  brushes  is  higher  than  that  of  the  two  batteries  in  series, 
then  battery  2  continuously  receives  charging  current,  and 
battery  i  is  alternately  discharged  and  charged  in  accordance 
with  the  closed  and  open  positions  of  the  ignition  apparatus. 
When  the  switch  is  closed  on  its  other  contact-point,  the  bat- 
tery 2  is  alternately  discharged  and  charged,  and  battery  i  is 
continuously  charged. 

97.  A  two-voltage  system  with  lamps  and  ignition  apparatus 
is  shown  in  Fig.  104.  The  voltage  at  the  lamps  is  approximately 
twice  that  at  the  ignition-apparatus  terminals.  At  the  lamps 


FLOATING  THE  STORAGE  BATTERY 


119 


the  voltage  is  approximately  equal  to  that  of  both  batteries  in 
series;  at  the  ignition  apparatus  the  voltage  is  approximately 
equal  to  that  of  one  battery.  If  there  were  no  loss  of  voltage 


Battery  1 

1 

+o 

Ignition 

Lar 

&     £ 

ips 
&    £ 

•      C 

ND.C. 
'Generator 

T3 

1             Apparatus 

F    -1     £/ 

It  ^ 

p2 

1 

1'  -J      Two-PointC 
Switch 

Battery  2 

- 

FIG.  104. 
Two-voltage  System  with  Lamps  and  Ignition  Appliances. 

in  the  connecting  wires,  the  voltage  at  the  lamps  would  be  the 
same  as  that  of  the  two  batteries  in  series;  and  that  at  the  ignition 
apparatus  would  be  equal  to  that  of  one  storage  battery. 

The  manner  of  operation  of  this  system  is  essentially  the  same 
as  that  of  Fig.  103. 

98.  A  switchboard  for  a  two-voltage  system,  a  direct-current 
dynamo,  and  two  storage  batteries  are  connected  together  in 
Fig.  105.  The  switchboard  has  an  ammeter  for  indicating  the 
amount  of  current,  and  a  voltmeter  for  measuring  the  pressure 
of  the  system.  There  is  also  a  pilot  lamp  which  glows  while  its 
circuit  is  closed  by  pressing  the  push-button  at  the  left-hand 
side  of  the  board.  The  voltmeter  is  made  to  register  by  pressing 
the  push-button  at  the  right-hand  side  of  the  board.  The  opera- 
tion of  the  system  is  essentially  the  same  as  that  of  Figs.  103 
and  104. 

The  board  has  five  switches,  all  of  the  blade,  or  knife,  type, 
whose  handles  are  shown  at  i,  2,  3,  4,  and  5. 

When  the  double-pole  double-throw  switch  i  is  closed  on  the 
dynamo  side  of  the  switchboard,  as  shown,  the  dynamo  sends 
current  through  both  storage  batteries  in  series  to  charge  them, 
and  at  the  same  time  supplies  current  to  the  12 -volt  lamp  circuits. 
Opening  the  switch  breaks  both  the  armature  circuit  of  the 


120 


ELECTRIC  IGNITION 


FIG.  105.     (See  also  Figs.  106  and  107.) 
Switchboard  Apparatus  and  Connections. 

dynamo  and  its  field-circuit,  and  also  breaks  the  battery  circuit 
to  the  i2-volt  lamps.  When  the  switch  is  closed  in  its  left-hand 
position,  the  battery  discharges  through  the  i2-volt  circuits  if 
the  lamps  are  turned  on.  The  connections  to  the  ignition  circuit 
are  not  affected  by  opening  or  reversing  the  main  switch  i. 


FLOATING  THE   STORAGE  BATTERY 


121 


Q<— Volt  Meter ->Q_ 


^ 

^ 

1    "? 

6  Volts  for  Ignition  Coils a>|rf  ^_12  Volts-> 

Lights 

Indicates  a  Closed  Switch 

FIG.  106.     (See  also  Figs.  105  and  107.) 
Wiring  Diagram  showing  Connections  at  the  Back  of  the  Switchboard. 

The  single-pole  double-throw  switch  2  is  for  cutting  the  am- 
meter into  or  out  of  circuit.  The  ammeter  is  in  circuit  when 
this  switch  is  in  the  position  shown.  Opening  this  switch  breaks 
either  the  main  circuit  of  the  dynamo  or  the  battery-discharge 
circuit,  according  to  the  position  of  the  main  switch  i. 

The  single-pole  double-throw  switch  3   is  for  reversing  the 


122 


ELECTRIC  IGNITION 


direction  of  the  6- volt  current  through  the  ignition  apparatus. 
When  the  switch  is  in  the  right-hand  position,  as  shown,  the 
ignition  apparatus  takes  current  from  battery  2  if  the  main 
switch  is  closed  in  the  battery-discharge  position.  If  the  ignition 
switch  3  is  closed  in  its  left-hand  position,  then  battery  i  supplies 
current  to  the  ignition  apparatus. 

The  single-throw  switches  4  and  5  are  for  opening  and  closing 
the  lamp  circuits. 

The  wiring  diagram  of  the  switchboard  is  shown  in  Fig.  106, 
which  also  shows  the  automatic  cut-out  for  protecting  the  dy- 


FIG.  107.     (See  also  Figs.  105  and  106.) 

Dynamo,  Storage  Battery  and  Switchboard.      Dayton  Electrical  Manufacturing 
Company,  Dayton,  Ohio. 

namo.  The  switch-blades  are  represented  by  broken  lines.  The 
double-throw  switches  are  represented  as  closed  in  the  reverse 
positions  of  the  preceding  figure.  The  diagram  shows  the  igni- 
tion apparatus  connected  to  the  positive  side  of  battery  i.  The 
ammeter  is  out  of  circuit,  and  both  the  main  circuit  and  the  field 
circuit  of  the  dynamo  are  open. 

Fig.  107  is  a  photographic  illustration  of  the  dynamo,  switch- 
board, and  two  6-volt  storage  batteries  such  as  are  used  in  a 
system  of  the  nature  just  described.  It  is  suitable  for  ignition 
and  lights  on  a  small  boat. 


CHAPTER  XII. 

MECHANICALLY   OPERATED   MAKE-AND-BREAK  IGNITERS  AND 
KICK-COILS  FOR  LOW-TENSION  IGNITION. 

99.  A  mechanically  operated  igniter  in  the  form  of  a  low- 
tension  ignition  plug  is  shown  in  Fig.  108  together  with  the 
means  of  operating  it.  The  illustration  is  elementary  in  its 


FIG.  108. 
Make-and-break  Igniter  or  Spark-Plug. 


Elementary  Form. 


nature.  Part  of  the  metal  plug  A  is  cut  away  to  show  the  con- 
struction. The  front  end  of  the  igniter  remains  outside  of  the 
cylinder  of  the  motor  when  the  igniter  is  in  place,  and  the  back 
end  either  projects  into  the  combustion  chamber  or  forms  part 

of  its  wall. 

123 


124  ELECTRIC  IGNITION 

A  metal  rod  B  extends  through  the  plug  and  is  enlarged  at 
the  inner  end  as  shown  at  C.  The  hole  through  which  this  bar 
passes  is  considerably  larger  than  the  bar  and  is  coned  at  the 
ends  to  fit  correspondingly  shaped  insulators  C  and  .D,  which 
hold  the  rod  in  place  and  insulate  it  from  the  plug  A.  When 
the  nut  E  is  screwed  down  it  draws  the  insulating  cones  C  and  D 
into  the  taper  ends  of  the  hole  in  the  plug  so  as  to  make  a  gas- 
tight  joint,  and  suitable  packing  around  the  rod  next  to  the 
enlarged  inner  end  and  under  the  nut  makes  tight  joints  at  these 
points. 

A  knurled  nut  F  at  the  outer  end  of  the  insulated  electrode  B 
affords  a  means  to  attach  the  wire  or  other  form  of  electric  con- 
ductor which  brings  the  current  to  the  plug.  The  screw  G  can 
be  used  for  attaching  the  other  wire  when  it  is  desired  to  bring 
both  sides  of  the  electric  circuit  to  the  igniter  in  this  manner. 
The  more  general  practice  is  to  connect  one  side  of  the  circuit 
to  the  metal  of  the  motor  at  the  most  convenient  point.  The 
metallic  contact  between  the  plug  and  the  motor  metal  gives 
electric  connection  also  between  them. 

A  movable  spindle  H  fits  in  another  hole  through  the  plug  so 
as  to  have  metallic  contact  with  the  plug,  and  at  the  same  time 
be  free  to  rotate,  or  rock,  in  the  body  of  the  plug.  The  inner 
end  of  the  spindle  has  a  metal  arm  /  rigidly  attached  to  it.  This 
arm  is  sometimes  called  the  movable  electrode.  Another  rocker- 
arm  J  is  fastened  rigidly  to  the  outer  end  of  the  spindle  H.  A 
blade-spring  K  is  fastened  to  the  rocker-arm  J  at  the  end  next 
the  spindle  H  and  is  of  such  a  form  that  its  free  end  stands  away 
from  the  arm  when  the  spring  is  not  stressed.  This  completes 
the  igniter  proper. 

When  the  outer  arm  J  is  raised  it  rocks  the  inner  arm  /  down 
so  that  it  makes  contact  with  the  inner  end  C  of  the  insulated 
electrode  B  and  thus  closes  the  electric  circuit  between  the  in- 
sulated electrode  and  body  A  of  the  plug.  Then  when  the  arm 
J  is  moved  downward  so  as  to  separate  the  movable  electrode 
from  contact  with  the  insulated  electrode,  an  electric  arc  is 
drawn  between  the  electrodes  C  and  /  at  the  point  where  the 
contact  is  broken. 


MAKE-AND-BREAK  IGNITERS  AND   KICK-COILS  125 

The  means  for  operating  the  igniter  consist,  as  shown,  of  a 
cam  L  and  a  cam-follower  M.  The  latter  is  in  the  form  of  a 
push-rod  with  a  collar  N  and  an  enlarged  spherical  upper  end  O. 
The  push-rod  passes  freely  through  suitable  openings  in  the  ends 
of  the  arm  /  and  spring  K.  The  spring  presses  lightly  down- 
ward against  the  collar  when  the  parts  are  in  the  position  shown. 
The  guide  P  is  for  keeping  the  push -rod  in  position.  The  cam 
is  driven  by  the  shaft  on  which  it  is  mounted. 

As  the  cam  L  rotates  in  the  direction  indicated  by  the  arrow 
on  it,  the  projecting  lobe  of  the  cam  lifts  the  push-rod  M  and 
then  allows  it  to  drop  when  the  edge  of  the  lobe  passes  from  under 
the  push-rod.  This  occurs  when  the  cam  has  passed  through 
about  three-quarters  of  a  revolution  from  the  position  in  which 
it  is  shown. 

The  upper  movement  of  the  push-rod  first  lifts  the  rocker-arm 
/  so  as  to  bring  the  movable  electrode  I  down  against  the  station- 
ary electrode.  The  movement  of  the  rocker-arm  is  stopped  as 
soon  as  the  movable  electrode  makes  contact  with  the  stationary 
one.  The  continued  upward  movement  of  the  push-rod  bends 
the  spring  K  and  the  rod  slips  up  through  the  arm  so  that  the 
enlarged  end  0  rises  above  the  arm.  When  the  edge  of  the  cam 
passes  from  under  the  push-rod,  the  reaction  of  the  spring  snaps  the 
push-rod  down  quickly  so  that  the  knob  on  the  upper  end  strikes 
the  rocker-arm  a  sharp  blow  and  drives  its  free  end  downward  so 
as  to  cause  a  rapid  separation  of  the  electrodes.  This  is  known  as 
the  hammer-break  method  of  interrupting  the  electric  current. 

The  rapid  separation  of  the  contact-points  of  the  igniter  is 
very  essential  to  the  successful  operation  of  the  igniter.  Com- 
pared with  slow  separation  of  the  contact-points,  the  rapid 
separation  produces  a  better  arc  for  ignition  and  causes  less 
fusing,  or  burning,  of  the  contact-points. 

The  insulation  used  in  the  igniter  is  generally  either  mica  or 
steatite  (soapstone).  The  mica  should  be  pure  and  especially 
free  from  any  metallic  substance  or  metallic  compounds.  When 
steatite  is  used,  it  is  generally  first  machined  to  form  and  then 
baked  at  a  high  temperature  to  bring  it  to  the  condition  in  which 
it  is  commonly  used  for  the  tips  of  gas  burners. 


126  ELECTRIC  IGNITION 

The  contact-pieces  (points)  of  the  igniter  are  generally  made 
of  either  platinum,  an  alloy  of  platinum  and  iridium  (platino- 
iridium),  of  steel  alloy,  especially  a  steel  alloy  containing  a  large 
proportion  of  nickel  together  with  less  amounts  of  other  elements. 
While  platinum  and  its  alloys  are  excellent  for  the  purpose,  they 
are  extremely  expensive.  Only  small  pieces  are  set  into  the 
electrodes,  and  are  generally  removable. 

100.  The  duration  of  contact  between  the  electrodes  of  a 
mechanically  operated  igniter  should  be  as  short  as  possible  to 
establish  current  flow  to  the  necessary  amount  when  the  source 
of  electricity  supply  is  a  battery.     Long  duration  of  contact  is 
wasteful  of  electricity  and  soon  exhausts  the  battery.     On  the 
other  extreme,  when  an  alternating-current  generator  supplies 
the  electricity  in  the  usual  manner,  the  electrodes  may  be  kept 
in  contact  continuously  except  during  the  time  necessary  to 
separate  them  to  form  the  arc  and  to  close  them  again  immedi- 
ately, so  far  as  current  supply  is  concerned.     When  electricity 
is  supplied  by  a  direct-current  generator,  it  is  generally  advisable 
to  have  a  short  period  of  contact,  since  imperfect  contact  main- 
tained for  some  time  may  cause  fusing  of  the  electrodes. 

Other  conditions,  such  as  the  use  of  several  igniters  in  the 
different  combustion  chambers  of  a  motor  with  several  cylinders, 
may  make  a  short  period  of  contact  necessary.  It  is  generally 
undesirable  to  have  the  electric  circuit  closed  through  two  or 
more  mechanically  operated  igniters  in  different  combustion 
chambers  at  the  same  instant.  In  some  ignition  systems  it  is 
impossible  to  operate  when  two  igniters  in  different  combustion 
chambers  have  their  electrodes  in  contact  at  the  same  instant. 

101.  Bosch  Mechanically  Operated  Igniter.  —  Fig.  109  shows 
two  views  of  an  igniter  and  operating  mechanism  as  constructed 
by  the  Bosch  Magneto  Company.     The  side  of  the  igniter  is 
shown  in  (a),  and  the  external  end  in  (b). 

A  coiled  tension-spring  A  acts  on  one  end  of  the  external 
rocker-arm  B  so  as  to  press  the  movable  electrode  C  against  the 
stationary  electrode  D  when  the  operating  rod  E  is  lifted  by  the 
cam  F.  The  operating  rod  E  is  pressed  downward  by  a  coiled 
compression  spring  G,  whose  lower  end  bears  against  a  collar  on 


MAKE-AND-BREAK  IGNITERS   AND   KICK-COILS 


127 


the  rod  and  whose  upper  end  bears  against  the  stationary  sup- 
port H. 

As  the  cam  F  rotates  it  lifts  the  operating  rod  E  against  the 
resistance  of  the  compression  spring  so  as  to  first  allow  the 
coiled  tension  spring  A  to  pull  the  contact-point  of  the  movable 
electrode  against  the  stationary  one,  and  then  to  push  the  rod 
up  still  farther  so  that  it  slips  through  the  hole  in  the  external 
rocker-arm.  The  enlarged  upper  end  of  the  rod  is  thus  lifted 


FIG.  109. 
Bosch  Make-and-break  Igniter.     Bosch  Magneto  Company,  New  York  City. 

free  from  the  rocker-arm.  As  the  cam  lobe  passes  from  under 
the  cam  follower,  the  operating  rod  E  is  forced  downward  by 
the  expansive  action  of  the  compression  spring  G,  and  the  ball 
at  the  top  of  the  rod  strikes  the  external  rocker-arm  and  moves 
it  down  so  as  to  quickly  separate  the  contact-points  of  the  elec- 
trodes. The  compression  spring  G  is  made  strong  enough  to 
overcome  the  resistance  of  the  tension  spring  A  and  keep  the 


128  ELECTRIC  IGNITION 

cam  follower  in  continuous  contact  with  the  cam  during  the 
highest  speed  at  which  the  igniter  is  to  be  used  in  any  particular 
application. 

The  lower  end  of  the  operating  rod  E  is  pin-connected  to  one 
end  of  each  of  a  pair  of  links  7  whose  opposite  ends  are  similarly 
connected  to  a  short  rocker-arm  on  the  shaft  J.  These  links 
carry  the  roller  K  which  bears  against  the  cam  and  follows  its 
outline.  The  short  rocker-arm  just  mentioned  can  be  rocked  by 
a  control  lever  L  fastened  to  the  same  shaft.  The  shaft  J  of 
the  controller  and  the  cam  shaft  are  supported  by  bearings 
which  are  maintained  in  fixed  positions  relative  to  the  igniter 
plug. 

The  control  lever  L  is  used  to  vary  the  instant  of  separation 
of  the  contact-points  of  the  electrodes  relative  to  the  rotative 
position  of  the  cam  and  to  the  position  of  the  piston  of  the  motor 
in  its  movement;  in  other  words,  to  advance  the  ignition  by 
causing  it  to  occur  earlier  in  the  revolution  of  the  cam,  or  to 
retard  it  by  causing  it  to  occur  later.  The  ignition  is  advanced 
by  moving  the  control  lever  to  the  right,  and  retarded  by  moving 
it  to  the  left.  The  dotted  outline  of  the  control  lever  to  the 
right  is  its  position  for  early  ignition,  and  the  dotted  outline  at 
the  left  is  its  position  for  late  ignition. 

102.  Truscott  Boat  Manufacturing  Company's  Igniter.  —  This 
igniter  is  used  especially  in  motor  boats.  It  is  shown  in  Fig.  no. 
The  outer  end  of  the  stationary  insulated  electrode  appears  at 
A .  This  electrode  extends  through  the  plug  in  the  usual  manner 
and  projects  inward  near  the  end  of  the  movable  electrode  B, 
which  is  fastened  to  a  rotative  spindle  whose  outer  end  is  shown 
at  C.  A  hammer-break  arm  D  fits  freely  rotatable  on  the  spindle 
C  and  is  normally  pressed  against  a  stop  on  the  spindle  by  a 
coiled  torsion  spring  E.  One  end  of  E  is  fastened  to  a  taper  pin 
which  passes  through  the  rocker-shaft. 

When  ignition  is  to  occur,  the  free  end  of  the  rocker-arm  D 
is  raised  by  the  lifter  G,  which  is  bored  to  fit  freely  rotatable 
on  the  end  of  the  push-rod  H.  As  the  arm  D  is  lifted  it  rocks 
the  spindle  C  and  contact  arm  B  with  it  until  the  contact-point 
in  B  strikes  against  the  stationary  electrode.  This  prevents 


MECHANICAL  MAKE-AND-BREAK  IGNITERS  129 

further  movement  of  both  the  rocker-arm  B  and  the  spindle  C, 
but  the  hammer-break  arm  D  is  lifted  still  higher  and  turns  on 
the  spindle  C  so  as  to  separate  itself  from  the  stop  on  the  spindle. 
The  lifting  of  D  winds  up  the  spring  E  to  a  slight  extent  more 
than  it  is  normally.  The  lifter-arm  H  continues  rising  till  it 
disengages  from  D.  The  spring  E  then  snaps  the  hammer-break 


H 


FIG.  no. 

Make-and-break  Igniter.    Truscott  Boat  Manufacturing  Company,  St.  Joseph, 

Michigan. 

arm  D  down  quickly  so  that  it  strikes  a  sharp  blow  against  the 
stop  on  the  spindle  C  and  causes  rapid  separation  of  the  ignition 
points.  The  downward  movement  of  D  continues  till  it  strikes 
the  arm  F  and  is  stopped  in  a  horizontal  position. 

The  lifter-rod  H  then  descends,  carrying  with  it  the  lifter  G, 
and  the  end  of  G  strikes  against  the  bevel  /  on  D.  The  end  of  G 
is  also  beveled  where  it  strikes  the  bevel  /.  The  action  of  the 
bevel  twists  G  around  on  H  as  they  descend,  so  that  G  slips  down 
past  D  and  is  then  snapped  back  under  D  by  the  coiled  tension 
spring  /  so  that  the  lifter  G  is  again  brought  into  position  to 
lift  D. 

K  and  K  are  nuts  on  the  stud-bolts  L  and  M  for  fastening  the 
igniter  to  the  motor.  The  lower  stud-bolt  M  is  extended  outward 


130 


ELECTRIC  IGNITION 


and  serves  as  a  binding-post  for  holding  one  of  the  wires  of  the 
external  circuit. 

Fig.  in  shows  the  mechanism  for  operating  the  push-rod. 
This  is  accomplished  by  an  eccentric  N  on  the  crank-shaft  0  of 


o 


FIG.  in. 
Operating  Mechanism  of  Fig.  no. 

the  motor.  The  eccentric  strap  P  is  connected  to  the  member 
Q  by  the  pin  R.  The  member  Q  is  fastened  to  the  lower  end  of 
the  push-rod  H  and  is  limited  to  vertical  movement  by  the 
plunger  S  which  fits  in  a  suitable  guide.  The  eccentric  has  a 
free  rotative  fit  on  the  crank-shaft  and  is  connected  to  the  arms 
of  a  fly-ball  governor  (not  shown)  also  mounted  on  the  crank- 


MECHANICAL  MAKE-AND-BREAK  IGNITERS  131 

shaft.  The  eccentric  is  thus  caused  to  rotate  with  the  crank- 
shaft so  as  to  move  the  push-rod,  but  its  angular  position  on  the 
crank-shaft  is  changed  by  the  action  of  the  governor  as  the  speed 
of  rotation  varies.  This  shifting  of  the  eccentric  varies  the  time 
of  ignition  so  that  it  occurs  earlier  at  high  speeds  of  rotation  than 
at  slow  speed.  When  the  motor  stops,  the  governor  brings  the 
eccentric  to  a  position  such  that  ignition  cannot  occur  before 
the  crank  of  the  motor  has  passed  its  dead-center  position  just 
after  compression  of  the  combustible  charge.  This  prevents 
ignition  at  such  an  instant  as  to  drive  the  crank-shaft  of  the 
motor  backward  when  starting  it. 

103.   The  Fay  &  Bowen  low-tension  igniter,  Fig.  112,  has  an 
adjustable  hammer-break  device  as  part  of  the  igniter.     Both 


FIG.  112. 
Fay  &  Bowen  Make-and-break  Igniter. 

the  stationary  electrode  A  and  the  movable  electrode  B  are 
provided  with  inserted  contact-pieces,  or  points.  The  hammer 
for  breaking  the  circuit  comprises  a  head  C  and  a  rod,  or  plunger, 
D.  The  latter  slides  through  holes  in  the  outer  end  of  the  body 
of  the  igniter,  and  is  pressed  against  the  cam  E  by  a  coiled  com- 
pression spring  F  which  is  wound  around  the  plunger  and  bears 
against  a  collar  on  it.  The  head  of  the  hammer  has  an  adjust- 
able striking  piece  G  which  is  pressed  against  the  external  arm 
H  of  the  movable  electrode  so  that  the  contact-points  of  the 
electrode  are  kept  apart  except  while  the  plunger  is  pushed  back. 
When  the  plunger  is  pushed  back  by  the  rotating  cam  E,  the 
coiled  tension  spring  7  draws  the  contact-point  of  the  movable 


132  ELECTRIC  IGNITION 

electrode  against  the  contact-point  of  the  stationary  electrode. 
The  tension  spring  /  is  connected  to  one  end  of  the  external  arm 
H  of  the  movable  electrode.  The  cam  forces  the  hammer  back 
far  enough  to  remove  its  striking  piece  to  some  distance  from 
the  arm  //.  When  the  edge  of  the  rotating  cam  passes  out  of 
engagement  with  the  plunger,  the  hammer,  including  the  plunger, 
is  snapped  down  by  the  spring  F  and  the  striking  piece  hits  the 
arm  H  so  as  to  drive  it  around  and  separate  the  contact-points 
of  the  electrodes  quickly. 

104.   Westinghouse  make-and-break  igniters  are  shown  in 
Fig.  113.     One  is  right-hand  and  the  other  left-hand.     The  mica 


FIG.  113. 
Low-tension  Igniter  of  the  Westinghouse  Machine  Company,  Pittsburg,  Pa. 

washers  for  insulating  the  stationary  electrode  at  the  outer  end 
are  visible  at  A .  The  inner  end  of  the  plug  is  recessed  to  receive 
similar  insulation.  The  contact-points  of  the  electrodes  are 
pressed  together  by  a  coiled  torsion  spring  wound  around  the 
rocker-spindle  of  the  movable  electrode  and  pressing  against  the 
outer  rocker-arm.  These  plugs  have  removable  contact-points 
in  the  electrodes. 


MECHANICAL  MAKE-AND-BREAK  IGNITERS  133 

105.  The  Snow  Steam  Pump  Works  mechanically  operated 
make-and-break  igniter  for  low-tension  current  is  shown  in 
Fig.  114.  The  cast-iron  plug  i  has  the  metal  cut  away  in  the 
middle  portion  to  secure  lightness  and  ease  of  construction.  A 
flange  at  the  outer  end  serves  as  a  means  of  supporting  some 
of  the  external  parts  and  for  fastening  the  plug  to  the  engine. 

The  movable  electrode  2  is  of  high-grade  nickel  steel  and  is 
one  piece  with  the  inner  rocker-arm  8  which  carries  the  removable 
contact-point  9.  The  inner  end  of  the  spindle  rocks  in  a  station- 
ary bronze  bushing  15,  and  the  outer  end  is  provided  with  a  tight- 
fitting  bronze  sleeve  17  which  rocks  in  a  steel  bushing  16.  The 
external  rocker-arm  is  fastened  to  the  spindle  by  a  bolt-and-nut 
lock. 

The  stationary  electrode  3  is  insulated  from  the  plug  by  mica 
washers  4  and  5,  and  lava  bushings  6  and  7.  It  is  held  in  place 
by  nuts  12  and  13,  which  also  hold  the  terminal  n  into  whose 
shank  is  soldered  the  wire  for  bringing  electricity  to  the  electrode. 
A  removable  contact-point  is  set  into  its  inner  end. 

Two  oil  pipes  20  connect  the  outer  end  of  the  plug  with  oil 
passages  leading  to  the  inner  bronze  bushing  15.  These  oil 
passages  are  shown  most  clearly  in  the  "  section  on  B-B." 

A  threaded  hole  22  through  the  flange  of  the  plug  is  for  the- 
insertion  of  a  cap-screw,  or  a  set-screw,  which  can  be  screwed 
down  to  press  its  point  against  the  metal  of  the  engine  and  thus 
forcibly  withdraw  the  plug  from  the  engine  to  a  short  distance 
after  the  fastenings  have  been  removed. 

The  outer  ends  of  two  of  these  igniters  with  all  attached  parts 
are  shown  in  Fig.  115.  The  reference  numbers  in  this  figure 
are  not  the  same  as  in  the  preceding  one. 

106.  The  mechanical  make-and-break  operating  mechanism 
of  the  Snow  Steam  Pump  Works  for  a  pair  of  igniters  in  the  same 
combustion  chamber  is  shown  in  Fig.  115.  The  igniters  are 
like  the  one  shown  in  the  preceding  figure. 

The  head  of  the  upper  igniter  is  shown  at  i,  and  that  of  the 
lower  one  at  2.  The  ends  of  the  insulated  stationary  electrodes 
of  the  two  igniters  are  at  3  and  4,  and  the  wire  terminals  for  the 
electric  conductors  are  shown  in  place  fastened  to  these  elec- 


134  ELECTRIC  IGNITION 


FIG.  114.     (See  also  Fig.   115.) 

Low-tension   Igniter.     Mechanical   Make-and-Break.     For   Large   Engine.     The 
Snow  Steam  Pump  Works,  Buffalo,  N.  Y. 

1.  Body  of  plug;  cast-iron. 

2.  Movable  electrode;  steel,  not  insulated. 

3.  Insulated  stationary  electrode,  steel. 

4.  5.   Mica  washers  for  insulating  stationary  electrode. 
6,  7.   Lava  insulating  bushings. 

8.  Inner  rocker-arm;  integral  part  of  rocker-shaft  2. 

9.  Contact-point;  movable  and  removable. 

10.  Contact-point;  stationary,  removable. 

11.  Terminal  to  which  electric  conductor  (wire)  is  soldered. 

12.  13.   Nuts  for  fastening  stationary  electrode  and  terminal  in  place. 

14.  External  rocker-arm  end.     Shown  better  in  Fig.  115  as  parts  5  and  6. 

15.  Bushing  for  rocker-arm  bearing;  stationary,  bronze. 

16.  Bushing  for  rocker-arm  bearings;  stationary,  steel. 

17.  Sleeve,  tight  on  2,  loose  in  14;  bronze. 

1 8.  Oil  hole. 

19.  Groove  for  oil  pipe. 

20.  Oil  pipe  leading  to  inside  bearing  of  rocker  shaft. 

21.  Stud-bolt  and  nut  for  fastening  igniter  to  engine.     Two  used. 

22.  Threaded  hole  in  flange  of  plug.     For  bolt  to  start  (loosen)  the  plug  to  remove 

it  from  the  engine. 


MECHANICAL  MAKE-AND-BREAK  IGNITERS 


22. 


OUTER  END  OF  PLUG 


22 


—  1 

j  

,1 

ll 

II 

j 

l! 

—  | 

i] 

i 

-i 

i 

i 

i 
i 

? 

-i 

— 

!'        '' 

l!    !i  '      i 

ten  <H  

L_J 

SIDE  OF  PLUG 


15 


LONGITUDINAL  SECTION  ON  A-A 


SECTION  ON  B-B  SECTION  ON  C-C 

FlG.    114. 


INNER  END 


136  ELECTRIC  IGNITION 

trodes  by  nuts.  The  external  rocker-arms,  or  tappet-arms,  5  <and 
6  are  in  positions  which  they  have  when  the  contact-points  of 
the  electrodes  are  touching  each  other.  The  contact-points  and 
inner  rocker-arms  are  represented  by  broken  lines.  The  coiled 
tension  springs,  7  for  the  upper  igniter  and  8  for  the  lower  one, 
connected  to  the  external  rocker-arms,  are  for  bringing  the  con- 
tact-points of  the  movable  electrodes  against  the  stationary 
contact-points. 

The  cam-shaft  9  has  fastened  to  it  a  cam-lobe  10,  which  pushes 
back  the  cam-follower,  or  push-rod,  n,  as  the  cam  rotates  in  the 
direction  of  the  arrow  on  the  cam-shaft.  The  push-rod  is  con- 
nected to  the  tappet-rod  13  by  means  of  the  pin  20.  The  tappet- 
rod  is  pin-connected  to  the  rocker-links  16  and  17,  which  swing 
on  stationary  shafts  18  and  19  respectively.  The  pin  20  makes 
the  connection  to  17,  and  a  similar  pin  connects  the  tappet-rod 
to  the  link  16. 

As  the  push-rod  n  is  forced  back  against  the  resistance  of 
the  coiled  compression  spring  21  by  the  action  of  the  cam,  the 
tappets  14  and  15  are  moved  away  from  the  tappet-arms  5  and  6. 
Then  when  the  cam-lobe  passes  out  of  engagement  with  the  push- 
rod,  the  latter  is  forced  quickly  toward  the  left  by  the  spring  2 1 . 
The  tappet-rod  and  tappets  follow  the  same  movement,  and  the 
tappets  strike  the  arms  5  and  6,  thus  causing  rapid  separation 
of  the  contact-points  of  the  electrodes.  The  push-rod  and 
attached  parts  continue  their  movement  toward  the  left  till  the 
buffer  25  strikes  the  stop-block  22.  The  push-rod  is  kept  in 
its  position  farthest  toward  the  left  by  the  action  of  the  spring 
21,  with  the  buffer  pressed  against  the  stop-block,  until  the  cam 
again  forces  the  push-rod  back  for  another  ignition.  The  con- 
tact-points of  the  electrodes  are  thus  kept  separated  and  the 
electric  circuit  broken  at  them  except  during  the  time  the  cam 
pushes  the  rod  back  as  far  and  farther  than  the  position  in  which 
the  push-rod  is  shown. 

The  time  of  ignition  can  be  adjusted  by  means  of  the  parts 
26  to  30  inclusive.  The  ignition  is  advanced  by  rotating  the 
hand-wheel  26  so  as  to  run  the  screw  farther  into  the  nut  27. 
This  movement  of  the  hand- wheel  forces  the  block  29  against 


Operating  Mechanism  for  Make-and-break  Igniter. 

Outer  end  of  upper  igniter  plug.  12. 

Outer  end  of  lower  igniter  plug.  13. 
Insulated  stationary  electrode  of  upper  igniter. 

Insulated  stationary  electrode  of  lower  igniter.  14, 
External  rocker-arm  of  upper  igniter. 

External  rocker-arm  of  lower  igniter.  16, 

8.   Coiled  tension  springs  for  drawing  contact-points  of  elec-       18, 

trodes  together.  20. 

Cam-shaft  or  lay-shaft.  21. 

Cam-lobe  for  operating  the  pair  of  igniters.  22. 
Cam  follower,  or  push-rod;  extends  up  to  the  yoke  12. 


FIG.  115.     (Se< 


Two  Igniters  Arranged  as  a 

Yoke  on  upper  end  of  push-i 
Tappet  rod,  pin-connected 

16  and  17. 
15.   Flanged  tappet  nuts  on  i 

5  and  6. 

17.  Upper  and  lower  rocker- 
19.  Stationary  shafts  suppor 
Pin  for  connecting  12,  13  an< 
Coiled  compression  spring  fo 
Stop-block  for  stopping  the 
shaft. 


SIDE  VIEW 


o  Fig.   114.) 

and  Operated  by  One  Push-Rod. 

e  yoke  12  and  the  rocker-links 
striking  the  igniter  rocker-links 

on  stationary  shafts  18  and  19. 
rocker-links  16  and  17. 

:irig  push-rod  n  toward  cam  10. 
on  of  push-rod  n  toward  cam- 


The  Snow  Steam  Pump  Works,  Buffalo,  N.  Y. 

23.  Bracket  for  holding  stop-block  22. 

24.  Guide,  flanged  at  right-hand  end. 

25.  Four  leather  washers  between  flange  on  guide  24  and  steel  wai 

next  to  22. 

26.  Hand-wheel  and  screw  for  adjusting  time  of  ignition. 

27.  Adjusting  nut  and  spring  sleeve;  held  by  stud  28. 

28.  Stud  for  supporting  27;  stationary. 

29.  Block  at  end  of  adjusting  screw. 

30.  Coiled  compression  spring  for  holding  push-rod  n  against  29 


MECHANICAL  MAKE-AND-BREAK   IGNITERS  137 

the  push-rod  and  moves  the  latter  toward  the  coiled  compression 
spring  30,  which  is  still  further  compressed  by  this  action.  Re- 
tarding the  ignition  is  accomplished  by  a  reverse  rotation  of  the 
hand-wheel.  The  nut  and  spring- tube  27  is  held  in  place  by 
the  stationary  stud-bolt  28. 

The  push-rod  swings  about  the  pin  20  as  a  hinge-joint  when 
the  rod  is  moved  sidewise  to  advance  or  retard  the  ignition.  In 
order  to  allow  this  motion  of  the  push-rod,  the  stop-block  22 
must  move  sidewise  in  its  supporting  bracket  23.  The  stop- 
block  has  a  sliding  fit  on  the  guide  24 which  is  fastened  to  the  push- 
rod.  The  bracket  is  cylindrically  curved  on  the  surfaces  that 
bear  against  the  stop-block  to  prevent  its  moving  in  the  direction 
of  the  length  of  the  rod,  the  center  of  curvature  being  coincident 
with  the  axis  of  the  pin  20  when  the  latter  is  in  the  position 
shown.  The  corresponding  bearing  surfaces  of  the  stop-block 
are  similarly  curved  to  fit  the  bracket. 

The  portion  of  the  mechanism  consisting  of  the  tappet-rod  13, 
and  the  rocker-links  16  and  17,  may  be  recognized  as  "  Watt's 
parallel  motion,"  which  causes  the  point  at  the  middle  of  the  axis 
of  the  push-rod  to  move  in  almost  exactly  a  straight  line  for  a 
short  distance  on  either  side  of  the  position  shown. 

107.  A  four-unit  low-tension  mechanism  with  one  make-and- 
break  igniter  for  each  of  four  combustion  chambers  is  shown  in 
outline  in  Fig.  116.  The  insulated  stationary  electrodes  are  i,  2, 
3,  and  4.  The  movable  electrodes  are  A,  B,  C,  and  D.  The 
corresponding  cams  are  #,  £,  c,  and  d,  all  on  the  same  shaft.  The 
full  line  GH  with  branches  leading  to  each  insulated  electrode 
represents  the  electric  conductors  for  carrying  current  to  the 
insulated  electrodes.  The  broken  line  with  branches  to  each 
rocker-spindle  of  the  movable  electrodes  is  to  indicate  that  all 
of  these  electrodes  are  electrically  connected  together  by  the 
metal  of  the  motor,  or  otherwise. 

The  cams  are  fixed  on  the  cam-shaft  at  equal  angles  with  each 
other  so  as  to  operate  the  igniters  at  regular  intervals  relative 
to  the  rotation  of  the  cam-shaft.  As  shown,  electrodes  A  and  i 
are  in  contact  with  each  other.  The  order  of  action  of  the  ig- 
niters, given  by  the  numbers  of  the  insulated  electrodes,  is  i,  3, 


138 


ELECTRIC  IGNITION 


4,  2  when  the  cams  are  fastened  to  the  cam-shaft  in  the  position 
shown. 


FIG.  116. 
Make-and-break  Igniters  Arranged  for  Four  Combustion  Chambers. 

108.  An  Allis-Chalmers  gas  engine  with  mechanical  make-and- 
break  low-tension  igniters  is  shown  in  Fig.  117,  reproduced  from 
a  photograph  of  the  engine.     The  four  igniters  are  at  i,  2,  3,  and 
4.    The  cam-shaft  5  lies  parallel  to  the  stroke  of  the  pistons  and 
carries  four  cams,  one  for  each  igniter.     It  is  driven  by  screw- 
gears  and  a  cross-shaft  in  the  casing  6.     Advance  and  retard  of 
ignition  is  effected  by  moving  one  of  the  screw-gears  along  its 
shaft  so  as  to  change  the  relative  rotative  positions  of  the  driving 
and  driven  shafts.     The  hand-wheel  7  is  for  shifting  the  screw- 
gear  to  adjust  the  ignition  as  described. 

Kick-Coils. 

109.  A  single-wound  kick-coil,  also  called  reactance  coil  and 
spark-coil  in  combustion-motor  practice,  is  used  in  connection 


KICK-COILS 


139 


W 


140  ELECTRIC  IGNITION 

with  low-tension  mechanical  make-and-break  ignition  systems 
in  order  to  obtain  a  good  electric  arc  between  the  contact-points 
of  the  igniter  when  current  is  supplied  by  a  battery,  also,  under 
some  conditions,  when  current  is  supplied  by  a  dynamo. 

A  kick-coil  consists  essentially  of  a  coil  of  insulated  copper  wire 
wound  in  several  layers  around  a  bundle,  or  sheaf,  of  small  wires 
of  mild  steel  or  soft  iron.  Fig.  118  shows  one  form  of  kick-coil. 


FIG.  118.  FIG.  119. 

Kick-Coil  with  the  Ends  of  the  Kick-Coil  with  Protective  Cap  over 

Core  Exposed.  Ends  of  Core. 

A  is  the  core  of  small  wires  of  soft  iron  or  mild  steel,  and  B  is 
the  coil  of  insulated  copper  wire.  The  core  and  wire  are  mounted 
on  a  wooden  frame  C.  The  ends  of  the  insulated  copper  wire 
of  the  coil  are  connected  to  binding  posts  D  and  E,  which  are 
the  terminals  of  the  coil.  The  kick-coil  is  neither  more  nor  less 
than  an  electromagnet,  but  it  takes  the  names  just  given  above 
on  account  of  the  use  to  which  it  is  applied. 

Fig.  119  is  another  kick-coil  in  which  the  ends  of  the  core  are 
covered  with  non-magnetic  caps  to  prevent  rusting. 

Other  forms  of  mountings  for  kick-coils  are  shown  in  Figs.  120 
and  121.  In  the  latter  the  coil  is  inclosed  in  a  water-tight  casing. 

The  sizes  of  the  kick-coils  found  in  use  vary  considerably, 
those  for  very  large  engines  being  larger  than  those  for  small 
ones.  The  average  size  is  about  6  inches  long  over  all,  with  a 
core  from  ij  to  ij  inches  diameter,  and  with  a  coil  from  3  to  3^ 
inches  long  containing  from  5  to  6  pounds  of  insulated  copper 
wire,  including  the  weight  of  the  insulation  on  the  wire.  The 
insulation  on  the  wire  is  generally  a  double  covering  of  cotton 


KICK-COILS 


141 


thread  such  as  is  ordinarily  used  for  insulating  magnet  wires. 
The  diameter  of  the  copper  wire  is  generally  that  corresponding 
to  No.  14  American  wire  gauge  (.064  inch),  or  somewhat  larger. 
The  electrical  resistance  of  the  coil  is  generally  in  the  neighbor- 
hood of  one  ohm.  These  dimensions  apply  to  coils  such  as  are 


FIG.  1 20. 
Kick-Coil.     Ordinary  Type. 


FIG.  121. 
Kick-Coil  Inclosed  in  Waterproof  Casing. 

used  with  small  stationary  engines.  Kick-coils  longer  in  propor- 
tion to  the  dimensions  just  given  are  sometimes  used,  but  they 
are  not  as  efficient  as  the  shorter  ones  of  equal  weight  and  elec- 
tric resistance. 

The  kick-coils  intended  for  use  in  damp  places,  as  on  open 
boats,  generally  have  the  insulation  on  the  wires  saturated  with 
waterproof  insulating  varnish  put  on  by  a  process  which  removes 
moisture  from  the  covering  wrapped  on  the  wires. 


142 


ELECTRIC  IGNITION 


110.  Screw-top  Kick-Coil.  A  kick-coil  with  a  screw  top  is 
shown  in  Fig.  122.  The  threaded  top  of  the  coil  can  be  screwed 
into  a  plate  such  as  is  sometimes  used  for 
a  battery  (see  Fig.  82).  The  size  of  the 
coil,  i\  by  6T3g  inches,  is  practically  the 
same  as  that  of  a  standard  dry  cell.  It 
can  therefore  be  put  into  the  screw-plate 
along  with  dry  cells,  occupying  the  same 
amount  of  space  as  one  of  the  cells.  The 
coil  is  also  provided  with  the  usual  form 
of  terminals  and  nuts,  so  that  wires 
can  be  connected  to  it  in  the  usual 
manner. 

111.  Tell-tale  Kick-Coil.  —  A  kick-coil 
with  a  tell-tale  for  visibly  indicating  the 
action  of  an  igniter  is  shown  in  Fig.  123, 
FlG  I22  in  both  side  and  end  views.     The  tell-tale 

Screw-top  Kkk-Coilto  go  in  consists  of  a  piece  of  mild  steel  A  sus- 
Battery  Case  with  Dry  pended  by  a  short  bar  B  which  swings 

Cells.    Stanley  &  Patter-  Qn    the    pin    C    that    passeg    through    the 
son,  New  York,  N.  Y.  ^      ,   ,,       ,  ,        ,         T         7^ 

upper  end  of  the  bar  and  a  bracket  D. 

The  latter  is  fastened  rigidly  to  one  of  the  caps  of  the  kick-coil. 
When  no  current  is  passing  through  the  kick-coil,  the  tell- 
tale hangs  in  the  position  shown  in  the  figure.     As  soon  as  cur- 


—  -, 
I 
1 

u 
^\J~B 

FIG.  123. 

Tell-tale  Kick-Coil. 

rent  sufficiently  large  for  contact  ignition  passes  through  the 
coil,  the  part  A  is  quickly  drawn  toward  the  core  of  the  coil 
by  magnetic  action.  The  tell-tale  falls  back  again  quickly  when 
the  current  is  interrupted,  as  by  the  separation  of  the  contact- 


KICK-COILS  143 

points  of  the  igniter.  The  kick-coil  is  placed  in  series  with  the 
igniter  when  used  in  a  make-and-break  ignition  system. 

If  any  trouble  prevents  the  igniter  from  closing  the  circuit 
so  that  the  necessary  amount  of  current  flows  for  satisfactory 
ignition,  then  the  action  of  the  indicator  is  sluggish  as  it  is  drawn 
toward  the  coil  core  if  some  small  amount  of  current  flows. 
If  no  current  flows  through  the  igniter,  the  tell-tale  has  no  motion. 
The  indicator  falls  back  sluggishly  if  the  breaking  of  the  circuit 
is  not  accomplished  quickly,  as  it  should  be  at  the  igniter  contact- 
points. 

The  tell-tale  is  therefore  an  indicator  of  whether  the  igniter 
is  operating  effectively,  improperly,  or  not  at  all. 


CHAPTER  XIII. 

MECHANICAL  MAKE-AND-BREAK  LOW-TENSION  IGNITION 

SYSTEMS. 

112.   A  battery,  a  reactance  coil,  and  a  make-and-break  igniter 

of  the  mechanically  operated  type  are  electrically  connected  to- 
gether in  Fig.  124  so  as  to  form  a  low-tension  ignition  system. 
All  of  the  parts  are  represented  conventionally.  Only  the  elec- 
trodes of  the  igniter  are  shown.  It  is  immaterial  whether  the 
battery  is  considered  a  primary  battery  or  a  storage  battery,  so 
far  as  the  principle  of  operation  of  the  system  is  concerned. 

The  positive  (+)  terminal  of  the  battery  is  connected  to  one 
of  the  terminals  of  the  kick-coil,  and  the  other  terminal  of  the 
coil  is  connected  to  the  insulated  electrode  61  of  the  igniter.  The 
negative  (— )  terminal  of  the  battery  is  electrically  connected 


ig-niter 

—*i 

"QS  I   IJIJUJ//I  Batter 


"Ground"  on  Metal  Structure 


FIG.  124. 
Elementary  Low-tension  Make-and-break  Ignition  System  with  Battery  Current. 

to  the  movable  electrode  M  of  the  igniter.  As  shown  in  the 
diagram,  the  negative  wire  from  the  battery  is  connected  at  F 
to  some  part  of  the  metal  structure  which  forms  part  of  the 
engine  or  of  the  metal  frame  to  which  the  metal  of  the  engine 
is  metallically,  and  therefore  electrically,  connected.  The  metal 
structure  is  customarily  referred  to  as  ground.  The  negative 
side  of  the  battery  may,  if  desired,  be  connected  by  a  wire  direct 
to  the  igniter.  Diagrams  in  which  the  metal  structure  is  used 
as  part  of  the  electric  circuit  involve  all  of  the  features  of  those 
in  which  the  frame  is  not  used  as  part  of  the  electric  circuit,  and, 
in  many  cases,  several  additional  features. 

144 


MECHANICAL  MAKE-AND-BREAK  IGNITION  SYSTEMS      145 

As  soon  as  the  electrodes  make  contact  with  each  other  so  as 
to  close  the  electric  circuit,  current  begins  to  flow  from  the 
positive  (+)  side  of  the  battery  through  the  kick-coil  (reactance 
coil),  the  igniter,  and  then  through  ground  back  to  the  negative 
side  of  the  battery.  When  the  electrodes  are  separated  to  break 
the  electric  circuit,  an  electric  arc  is  formed  between  the  contact- 
points  momentarily  at  the  instant  of  separation.  This  arc  will 
ignite  a  combustible  mixture  of  gases. 

The  reactance  coil  is  placed  in  the  circuit  in  order  to  secure 
a  sufficiently  strong  arc  with  a  small  current  from  a  battery  of 
low  voltage.  The  pressure  at  the  battery  terminals  is  generally 
not  more  than  six  volts.  The  current  seldom  exceeds  five  am- 
peres and  is  often  less  than  two  amperes.  It  is  probably  usually 
between  one  and  two  amperes.  With  this  pressure  and  current, 
only  a  very  minute  arc,  or  spark,  can  be  obtained  without  the 
aid  of  a  reactance  coil. 

The  stronger  arc  obtained  with  the  reactance  coil  in  circuit 
is  due  to  the  inductive  action  of  the  coil.  Breaking  the  circuit 
at  the  igniter  causes  an  immediate  decrease  in  the  current.  The 
magnetic  strength  of  the  core  of  the  reactance  coil  decreases  in 
consequence  of  the  decrease  of  current  in  the  winding  of  the  coil. 
This  decrease  of  magnetism  in  the  core  reacts  to  prevent  rapid 
decrease  of  current  in  the  winding.  The  decrease  of  current  in 
each  turn  of  the  coil  also  reacts  inductively  to  prevent  rapid 
decrease  of  current  in  the  other  turns  of  the  winding.  The  total 
effect  of  the  reactance  coil  is  to  cause  the  current  to  flow  longer, 
both  in  time  and  distance,  across  the  gap  formed  between  the 
electrodes  by  separating  them  than  when  no  reactance  coil  is  used. 

Although  no  switch  for  opening  and  closing  the  circuit  by 
hand  is  shown  in  the  diagram,  one  can  be  put  in  at  any  convenient 
point. 

113.  The  duration  of  contact  between  the  electrodes  of  the 
igniter  should  be  as  short  as  possible  with  satisfactory  operation 
when  a  battery  supplies  the  current.  This  in  order  to  secure 
economy  of  current  and  long  life  of  the  battery.  The  circuit 
must  be  kept  closed  long  enough,  however,  to  allow  the  current 
to  become  sufficiently  strong  to  make  a  good  arc  when  the  elec- 


146 


ELECTRIC  IGNITION 


trodes  are  separated.  The  reactance  coil  prevents  the  current 
from  reaching  its  full  strength  as  quickly  as  it  would  if  there 
were  no  reactance  in  the  circuit.  The  coil  prevents  rapid  in- 
crease of  current  as  well  as  rapid  decrease. 

114.   A  magneto  and  a  make-and-break  igniter  are  connected 
together  as  parts  of  a  low- tension  ignition  system  in  Fig.  125. 


Cain 


"Ground"  on  Metal  Structure 


A.C.  Magneto 
Armature/ 


FIG.  125. 

Elementary  Make-and-break  Low-tension  Alternating-current  Magneto  Ignition 

System. 

The  magneto  is  of  the  shuttle-wound  alternating-current  type, 
and  the  igniter  is  mechanically  operated.  The  operating  mechan- 
ism is  of  the  type  shown  in  Fig.  108. 

The  insulated  end  of  the  armature  winding  of  the  magneto  is 
electrically  connected  to  the  insulated  electrode  S  of  the  igniter 
by  a  wire.  This  is  the  only  connection  necessary  between  them 
if  the  frame  or  base-plate  of  the  magneto  is  set  on  a  metallic 
structure  which  has  metallic  (electric)  connection  with  the 
igniter.  If  the  magneto  is  mounted  on  a  non-metallic  base 
which  is  not  a  conductor  of  electricity,  then  electric  connection 
between  the  magneto  and  the  metal  structure  or  the  igniter 
must  be  provided. 

The  magnets  and  pole-pieces  of  the  magneto  should  not  have 
contact  with  or  be  very  close  to  a  piece  of  iron  or  steel,  such  as 
part  of  the  frame  of  the  motor.  It  is  generally  best  to  have  no 
iron  or  steel  connection  whatever  between  the  magnets  and  an 
iron  or  steel  part  of  the  structure  on  which  the  magneto  is 


MECHANICAL  MAKE-AND-BREAK   IGNITION  SYSTEMS      147 

mounted.  The  base  of  the  magneto,  or  the  straps  or  other  form 
of  fastening  for  attaching  the  magneto  to  a  steel  structure,  can 
be  of  any  non-magnetic  metal  or  alloy.  Brass,  bronze,  and 
aluminum  alloy  are  commonly  used  for  this  purpose. 

Low-tension  alternating-current  magnetos  intended  for  igni- 
tion usage  generally  have  only  one  terminal  for  making  external 
connection.  In  case  there  are  two  terminals,  one  can  be  con- 
nected to  the  metal  structure  (ground)  or  to  the  igniter  direct, 
and  the  other  to  the  insulated  electrode  of  the  igniter  in  the  usual 
manner.  The  latter  has  been  described. 

The  igniter  must  operate  in  synchronism  with  the  production 
of  maximum  electromotive  force,  or  pressure,  in  the  magneto, 
since  a  suitable  arc  can  be  formed  only  when  there  is  sufficient 
pressure  to  cause  a  flow  of  current  large  enough  to  produce  an 
arc  of  the  desired  strength.  If  the  magneto  armature  rotates, 
and  a  one-lobe  cam  such  as  is  shown  in  the  figure  is  used  to 
operate  the  igniter,  then  the  cam  may  rotate  at  twice  the  speed 
of  the  armature,  so  as  to  draw  an  electric  arc  at  each  half -revo- 
lution of  the  magneto  armature,  which  is  as  frequently  as  an  arc 
can  be  drawn  when  the  magneto  is  of  the  type  shown.  Or  the 
cam  may  rotate  at  the  same  speed  as  the  armature,  so  that  an 
arc  is  drawn  at  every  second  production  of  maximum  pressure  in 
the  magneto. 

It  is  customary  to  have  a  one-lobe  cam  make  either  two,  one, 
or  one-half  revolution  for  each  revolution  of  the  magneto  arma- 
ture when  the  magneto  produces  two  impulses  per  revolution 
of  its  armature.  This  applies  to  a  magneto  of  the  type  shown 
in  the  figure.  If  a  magneto  which  gives  four  impulses  per 
revolution  of  its  rotor  is  used,  then  the  one-lobe  cam  may  make 
either  four,  two  or  one  revolution  per  revolution  of  the  magneto 
rotor. 

It  is  not  necessary,  on  account  of  economy  of  current,  to  limit 
the  time  during  which  the  circuit  is  closed  by  keeping  the  elec- 
trodes of  the  igniter  in  contact  with  each  other  when  current 
is  supplied  by  an  alternating-current  magneto,  since  the  magneto 
does  not  supply  current  continuously  and  there  is  no  need  of 
securing  economy  of  current. 


148  ELECTRIC  IGNITION 

No  reactance  coil  is  required  in  connection  with  an  alternating- 
current  magneto.  The  armature  of  the  magneto  acts  as  a 
reactance  to  produce  a  strong  arc  at  the  ignition  points.  A 
switch  can  be  placed  at  any  convenient  point  in  the  circuit 
for  opening  the  circuit  to  stop  ignition,  or  a  switch  between 
ground  and  the  wire  leading  to  the  igniter  may  be  closed  to  stop 
ignition. 

115.  A  direct-current  generator,  a  kick-coil,  and  a  mechanical 
make-and-break  igniter  are  connected  together  for  a  low-tension 


FIG.  126. 
Elementary  Make-and-break  Ignition  System  with  Direct-current  Generator. 

ignition  system  in  Fig.  126.  The  generator  is  represented  only 
by  its  commutator  and  brushes. 

The  positive  brush  of  the  generator  is  connected  to  one  ter- 
minal of  the  reactance  coil,  and  the  other  terminal  of  the  coil 
is  connected  to  the  insulated  electrode  S.  The  negative  brush  of 
the  generator  is  connected  to  the  metallic  ground  of  the  structure. 
This  system  is  the  same  as  that  in  Fig.  124  except  the  use  of  a 
direct-current  generator  instead  of  a  battery,  and  the  same 
statements  apply  regarding  the  manner  in  which  connections 
may  be  made. 

A  generator  giving  a  pressure  of  five  volts  and  having  a  capac- 
ity of  five  amperes  is  suitable  for  this  system.  The  current 
capacity  may  be  even  less  than  five  amperes.  The  field-magnets 
of  the  generator  may  be  either  permanent  magnets  or  electro- 
magnets. If  of  the  latter  type,  they  may  be  either  plain  shunt- 
wound  or  compound- wound.  The  shunt- wound  type  is  less 
expensive  to  construct  and  is  entirely  satisfactory.  Either  of 
the  electromagnetic  types  requires  some  time  to  pick  up  its 
magnetism  after  starting,  and  is  therefore  not  very  convenient 
to  use  in  connection  with  an  isolated  motor  which  must  be  de- 


MECHANICAL  MAKE-AND-BREAK  IGNITION  SYSTEMS      149 

pended  on  to  drive  the  ignition  generator,  unless  a  battery  is 
provided  for  ignition  while  starting  the  motor. 

Direct-current  generators  do  not  always  have  enough  inductive 
action  to  be  used  without  a  reactance  in  the  circuit.  A  hand- 
switch  may  be  put  in  the  circuit  where  desired. 

116.  System  for  Four  Combustion  Chambers.  Mechanical 
Make-and-break  Igniter,  Storage  Battery,  Primary  Battery,  and 
Direct-current  Generator.  — Fig.  127  shows  connections  for  four 
low-tension  igniters,  one  for  each  of  four  combustion  chambers, 
to  which  current  can  be  supplied  either  by  a  direct-current 
generator,  a  primary  battery,  or  a  storage  battery,  using  only 


Primary  Battery 


FIG.  127. 

Make-and-break  Ignition  System  for  Four  Combustion  Chambers  and  Having 
Three  Sources  of  Current  Supply. 

one  at  a  time.  This  system  is  applicable  to  a  four-cylinder 
single-acting  motor,  or  to  a  double-acting  engine  with  two 
cylinders. 

The  switch-arm  F  is  pivoted  at  0  and  its  free  end  can  be  moved 
into  position  to  bear  against  either  of  the  contact-points  G,  L, 
or  P  of  the  switch.  The  arm  is  shown  in  the  position  to  use 
the  generator.  The  switch-points  G,  P,  and  L  should  be  far 
enough  apart  to  keep  the  arm  from  making  contact  with  two 
of  them  at  the  same  time  while  shifting  it  from  one  point  to 
another. 

It  is  immaterial  whether  the  positive  or  the  negative  sides  of 
the  generator  and  batteries  are  connected  to  the  switch,  but 
it  is  advisable  to  have  either  all  of  the  positive  or  all  of  the  nega- 
tive terminals  connected  to  it,  since  there  is  then  less  chance  of 


150  ELECTRIC  IGNITION 

injury  to  the  batteries  in  case  electric  connection  is  accidentally 
made  between  the  switch-points,  or  if  the  insulation  of  the  switch 
becomes  poor  so  that  leakage  of  current  may  occur.  If  G  were 
connected  to  the  positive  of  the  generator  and  L  to  the  negative 
of  the  storage  battery,  then  if  G  and  L  were  electrically  connected 
together  an  excessive  current  would  flow  through  the  generator 
and  storage  battery  in  series.  The  path  of  this  current  would 
be  through  the  connections  to  the  switch-points  G  and  L,  and 
the  ground  connections  of  the  generator  and  storage  battery. 
Little  or  no  current  would  flow  through  the  igniters,  and  there 
would  be  no  ignition  in  consequence.  A  similar,  but  less  severe, 
action  would  occur  if  the  positive  of  the  generator  were  connected 
to  the  negative  of  the  primary  battery,  or  the  positive  of  the 
storage  battery  to  the  negative  of  the  primary  battery. 

The  storage  battery  is  not  floated  on  the  line,  and  therefore 
must  be  charged  from  some  separate  source  of  current  supply. 
The  generator  shown  might  be  used  to  charge  the  storage  battery 
by  connecting  them  together  properly  with  a  suitable  rheostat 
or  other  current-regulating  device  in  the  circuit. 

An  electric  arc  can  be  obtained  at  only  one  of  the  igniters  at 
a  time.  If  two  igniters  are  closed  and  then  one  opened,  no  arc 
will  be  formed  between  the  electrodes  during  their  separation. 
This  system  can  be  extended  to  any  number  of  igniters,  provided 
only  one  igniter  has  its  electrodes  in  contact  at  any  instant. 

117.  An  alternating-current  magneto,  a  primary  battery,  and 
four  mechanical  make-and-break  igniters  are  used  in  the  low- 
tension  system  of  Fig.  128.  When  the  switch  is  closed  on  its 
contact-point  L  as  shown,  current  is  furnished  by  the  magneto 
only.  The  battery  and  the  reactance  coil  are  both  cut  out  of 
circuit.  By  moving  the  switch-arm  up  to  its  contact-point  P 
the  magneto  is  cut  out  of  circuit,  and  the  primary  battery  alone 
furnishes  current.  When  the  battery  is  used,  the  current  passes 
through  the  reactance  coil,  but  not  when  the  magneto  is  fur- 
nishing the  current.  This  system  can  be  used  in  the  same 
manner  as  that  of  Fig.  127,  and  is  subject  to  the  same  restrictions 
regarding  two  or  more  igniters  being  in  the  closed  position  at 
the  same  time. 


MECHANICAL  MAKE-AND-BREAK   IGNITION   SYSTEMS      151 


j    Igniters 


on_Metal__ 

Primary  Battery 


FIG.  128. 

Four-igniter  Low-tension  Ignition  System  with  Primary  Battery  and  Alternating- 
current  Magneto. 

118.  A  storage  battery  "  floated  on  the  line  "  of  a  shunt- wound 
direct-current  generator,  and  mechanical  make-and-break  igni- 
ters, are  used  in  the  system  of  Fig.  129.  The  current  to  the  ig- 


"Ground' 


Igniters 


F 

Reactance 

o  2 

Storage 
Battery 

O 

*  ° 

t 

\}\ 

J 

IA 

FIG.  129. 

Ignition  System  with  Four  Low-tension  Igniters  and  a  Storage  Battery  Floated 

on  the  Line. 

niters  always  passes  through  the  reactance  coil.  The  use  of  a 
storage  battery  in  conjunction  with  a  generator  in  this  manner 
has  been  discussed  in  earlier  paragraphs. 

No  switches  for  opening  the  circuit  are  shown,  but  if  one  is 
placed  between  A  and  the  automatic  cut-out,  or  between  the 
negative  brush  and  the  "  ground  "  connection  at  B,  it  will  cut 
out  the  generator  from  the  system  but  will  not  stop  the  current 
through  the  field-coils  of  the  generator.  A  switch  between  the 
storage  battery  and  either  A  or  E  will  cut  out  the  battery  com- 
pletely. One  between  A  and  F  will  cut  off  all  the  current  from 


152 


ELECTRIC  IGNITION 


the  igniters.  When  this  last  switch  is  open  and  the  other  two 
closed,  the  generator  will  charge  the  battery  if  the  pressure  at 
the  brushes  of  the  generator  is  higher  than  that  of  the  battery. 
119.  no-volt  Generator  and  6-volt  Primary  Battery  Mechani- 
cal Make-and-break  System.*  —  Fig.  130  is  a  system  in  which 
a  no- volt  direct-current  generator  is  driven  by  the  gas  engine 


FIG.  130. 

Make-and-break  Ignition  System  Using  a  6-volt  Primary  Battery  and  a  no- volt 

D.  C.  Generator. 

to  which  it  furnishes  ignition  current.  A  primary  battery  is 
provided  for  starting,  since  no  current  is  available  from  the 
generator  till  it  is  well  up  to  normal  speed. 

The  chief  items  of  the  system,  as  furnished  by  the  Westing- 
house  Machine  Company,  are: 

A.   Combination  switchboard. 

BBB.  Three  no- volt  i6-candle-power  incandescent  lamps 
with  carbon  filament. f 

*  The  diagrams  shown  in  Figs.  130,  133,  135,  136,  137,  and  139  are  slightly 
modified  forms  of  those  used  by  the  Westinghouse  Machine  Company.  They 
have  been  modified  only  enough  to  make  them  conform  with  the  conventions 
used  in  this  book.  This  modification  does  not  change  the  ignition  system. 

t  If  incandescent  lamps  having  filaments  or  "  pencils  "  of  other  material  than 
carbon  are  used,  the  lamps  should  be  of  a  size  requiring  the  same  amount  of  cur- 
rent as  the  carbon-filament  lamps  specified.  Any  non-inductive  resistance  can 
be  used  in  place  of  the  lamps,  the  only  requirement  being  that  the  amount  of 
resistance  shall  be  the  same  as  that  of  the  lamps  specified. 


MECHANICAL  MAKE-AND-BREAK  IGNITION  SYSTEMS     153 

C.  1 1 o- volt  shunt- wound  dynamo. 

D.  Edison  primary  battery,  6  cells. 

The  igniter  M  is  part  of  the  gas  engine.  Any  number  of 
igniters  can  be  used,  provided  only  one  has  its  electrodes  in 
contact  with  each  other  at  any  instant.  In  other  words,  not 
more  than  one  igniter  should  be  in  the  closed  position  at  any 
instant. 

The  switchboard  has  two  double-pole  double-throw  switches. 
The  one  at  the  right  is  called  the  dynamo  switch.  It  is  shown 
closed  in  its  up-position  with  the  handle  at  the  top.  The  left- 
hand  one  is  the  battery  switch.  It  is  standing  open  in  a  hori- 
zontal position  perpendicular  to  the  vertical  board.  The  handle 
appears  as  a  circle. 

Double-throw  switches  are  used  in  order  to  reverse  the  direc- 
tion of  current  through  the  electrodes  of  the  igniter.  The  object 
in  reversing  the  current  is  to  secure  equal  rapidity  of  wear  on 
the  contact-points  of  the  igniter.  There  is  a  tendency  for  one 
contact-point  to  wear  more  rapidly  than  its  mate  when  the  cur- 
rent always  flows  in  the  same  direction  through  the  igniter.  The 
contact-point  connected  to  the  positive  side  of  the  circuit  wears 
more  rapidly,  other  conditions  being  equal  for  the  two  points. 

When  the  switches  are  positioned  as  in  Fig.  130,  the  battery 
is  cut  out  of  circuit  and  the  generator  is  in  circuit  so  that  its 
positive  brush  is  connected  to  ground. 

The  switchboard  connections  back  of  the  board  are  shown  in 
Fig.  131.  The  wiring  is  shown  as  if  seen  from  the  front  through 
a  transparent  board.  The  reference  letters  are  the  same  as  in 
the  preceding  figure.  A  reactance  coil  is  incorporated  in  the 
switchboard.  The  switch-blades  of  the  dynamo  switch  are 
hinged  to  the  middle  terminals  i  and  2  of  that  switch. 

When  the  dynamo  switch  is  closed  in  the  up-position  as  in 
Fig.  130,  the  current  from  the  positive  brush  of  the  dynamo 
follows  the  path:  Positive  brush,  5,  4,  through  switch-blade  to  2, 
ground,  igniter  M,  reactance  coil,  lamps  BBB,  then  through  the 
connection  to  i,  switch-blade  to  3,  negative  brush  of  dynamo. 
If  the  switch  is  thrown  to  its  lower  position  with  its  handle 
down,  the  path  of  the  current  is  then:  Positive  brush,  5',  i,  lamps 


154 


ELECTRIC  IGNITION 


BBB,  reactance  coil,  insulated  electrode  of  igniter  M,  ground,  2, 
6,  3,  negative  brush  of  dynamo. 

When  the  battery  switch  is  closed  and  that  for  the  dynamo 
open,  the  current  does  not  flow  through  the  lamps.  If  the 
battery  switch  is  closed  in  its  up-position,  the  path  of  the  current 


FIG.  131. 
Switchboard  Connections  for  Fig.  130. 

is:  Positive  of  battery,  12,  9,  7,  ground,  igniter  M,  reactance  coil, 
8,  10,  negative  of  battery. 

The  amount  of  current  that  flows  through  the  igniter  when 
the  dynamo  alone  is  delivering  current  is  regulated  by  the  lamps. 
The  three  lamps  specified,  no- volt,  i6-candle-power,  carbon- 
filament,  will  allow  a  current  of  1.5  to  2  amperes  to  flow  through 
the  igniter,  according  to  the  efficiency  of  the  lamps.  This  is 
three  times  the  current  that  flows  through  one  lamp,  since  they 
are  in  parallel  with  each  other.  The  current  flows  through  the 


MECHANICAL  MAKE-AND-BREAK  IGNITION  SYSTEMS      155 

lamps  only  while  one  of  the  igniters  is  closed.  The  lamps  flash 
once  for  each  ignition  when  using  dynamo  current. 

When  the  battery  alone  is  in  use,  the  lamps  remain  dark. 

If  both  switches  are  closed,  the  generator  will  send  current 
through  the  battery,  at  least  during  the  time  all  of  the  igniters 
are  open.  Although  this  is  not  noticeably  injurious  if  continued 
for  only  a  short  time,  the  primary  battery  will  be  injured  if  both 
switches  are  left  closed  during  a  long  period  of  running. 


FIG.  132. 
Switchboard  Details  for  Fig.  130. 

Fig.  132  shows  front  and  side  views  of  the  switchboard  as 
constructed.  The  lamps  are  not  shown,  but  the  lamp  sockets 
appear. 

120.  Multiple  System  with  Switchboards,  Primary  Batteries, 
and  no-volt  Direct-current  Generator.  —  The  system  in  Fig.  133 
is  for  two  engines.  Two  switchboards  of  the  kind  just  described 
are  connected  to  one  generator.  Each  switchboard  has  its 


156 


ELECTRIC  IGNITION 


own  primary  battery.     Fuse-blocks  E  are  placed  between  each 
switchboard  and  the  generator. 

The  system  can  be  used  either  for  two  engines  or  for  dual 
ignition  in  one  engine.  In  the  latter  case,  two  igniters  are  placed 
in  each  combustion  chamber.  The  two  igniters  in  one  com- 


FIG.  133. 

Two  Switchboard  Units  for  Distributing  Current  to  Two  Sets  of  Low-tension 

Igniters. 


bustion  chamber  are  closed  and  opened  simultaneously,  so  that 
two  ignition  arcs  are  drawn  in  that  combustion  chamber  at  the 
same  instant. 

The  system  can  be  extended  to  any  number  of  switchboards 
and  the  corresponding  number  of  engines  or  of  igniters  in  each 
combustion  chamber  of  one  engine. 

The  wiring  diagram  is  shown  in  Fig.  134,  in  which  each  switch- 
board has  four  igniters.  Two  igniters,  M  and  M,  one  connected 
to  each  switchboard,  are  shown  closed,  which  is  allowable  in 
operation.  Any  igniter  of  one  switchboard  may  be  closed  during 
the  same  time  as  any  igniter  of  the  other  switchboard. 

The  dynamo  switches  must  both  be  closed  either  in  the  up- 
position,  as  shown  in  Fig.  133,  or  both  in  the  down-position, 
when  the  igniters  connected  to  both  boards  are  put  into  operation 


MECHANICAL   MAKE-AND-BREAK   IGNITION   SYSTEMS      157 


I 

•s 

I 


2  , 


158  ELECTRIC  IGNITION 

and  while  they  are  operating  on  current  from  the  dynamo.  If 
one  dynamo  switch  is  closed  in  the  up-position,  then  closing  the 
other  dynamo  switch  in  the  down-position  will  short-circuit  the 
dynamo,  and  one  of  the  fuses  at  the  fuse-blocks  E  will  be  melted 
or  "  blown,"  thus  opening  the  dynamo  circuit  through  one 
switchboard.  The  blowing  of  the  fuse  will  stop  ignition  by  the 
igniters  connected  to  that  board,  unless  the  battery  switch  on 
the  board  is  closed. 

If  the  dynamo  switch  on  board  i  is  closed  in  the  up-position, 
and  the  dynamo  switch  on  board  2  is  closed  in  the  down-position, 
then  the  positive  brush  of  the  generator  is  connected  direct  to 
ground  through  board  i,  and  the  negative  brush  of  the  generator 
is  connected  direct  to  ground  through  board  2,  thus  short-cir- 
cuiting the  generator  as  stated.  A  similar  short  circuit  is  made 
by  reversing  both  of  the  dynamo  switches  from  the  positions 
just  mentioned.  The  primary  battery  switch  alone  on  one 
board  can  be  left  closed  any  length  of  time  commensurate  with 
the  capacity  of  the  battery,  while  either  the  dynamo  switch  or 
the  battery  switch  is  closed  on  the  other  board,  or  boards. 

Reversing  the  dynamo  switches  during  the  operation  of  the 
system  can  be  safely  accomplished  by  first  closing  the  battery 
switch  on  any  one  of  the  boards  and  then  opening  the  dynamo 
switch  on  the  same  board.  This  should  be  done  successively 
for  all  of  the  switchboards.  The  dynamo  switches  can  then 
be  closed  in  their  reverse  position,  all  of  course  being  closed 
either  up  or  down. 

The  battery  switch  on  each  board  can  be  opened  as  soon  as 
the  dynamo  switch  on  the  same  board  is  closed,  or  the  battery 
switches  can  all  be  left  closed  till  all  of  the  dynamo  switches  are 
reversed,  and  then  all  of  the  battery  switches  can  be  opened. 

Specifically,  for  two  boards,  the  reversal  of  the  dynamo 
switches  can  be  done  as  follows,  referring  to  Fig.  133,  in  which 
the  battery  switches  are  closed  in  the  up-position  and  the  battery 
switches  are  open :  Close  battery  switch  on  board  i  in  either  the 
up-  or  down-position;  open  dynamo  switch  on  board  i;  close 
battery  switch  on  board  2  in  either  the  up-  or  down-position; 
reverse  the  dynamo  switch  on  board  2  to  the  down-position; 


MECHANICAL  MAKE-AND-BREAK  IGNITION  SYSTEMS      159 

open  the  battery  switch  on  2;  close  the  dynamo  switch  on  i  in 
its  down-position;  open  the  battery  switch  on  i. 

When  there  are  more  than  two  switchboards,  the  reversal  of 
the  dynamo  switches  can  be  carried  out  in  a  similar  manner, 
leaving  all  of  the  dynamo  switches  open  till  that  of  the  last  board 
is  reached,  then  reversing  it  and  afterward  closing  the  dynamo 
switches  of  the  other  boards  and  opening  the  battery  switches. 

121.  Storage  Battery  and  no-volt  Generator  Mechanical 
Make-and-break  System.  —  Referring  again  to  the  diagrams  of 
Figs.  130  and  131  for  one  switchboard,  a  6-volt  storage  battery 
may  be  substituted  for  the  primary  battery  D.  Then,  if  the 
dynamo  switch  and  the  battery  switch  are  both  closed  in  either 
the  up-position  or  the  down-position,  the  dynamo  will  send  cur- 
rent through  the  storage  battery  to  charge  it  during  the  time 
the  igniters  are  all  open.  While  an  igniter  is  closed  current  will 
flow  through  it,  and  the  breaking  of  the  circuit  by  separating 
the  contact-points  of  the  igniter  will  draw  an  arc  for  ignition. 

If  the  generator  stops  accidentally,  as  on  account  of  the  break- 
age of  a  belt  for  driving  it,  the  storage  battery  furnishes  current 
so  that  no  interruption  of  ignition  occurs.  This  when  the 
switches  are  both  closed  before  the  accident.  No  automatic 
cut-out  is  necessary  to  protect  the  generator  from  excessive 
current  sent  through  it  when  the  generator  stops.  The  lamps 
limit  the  current  that  the  battery  can  send  through  the  generator 
in  such  a  case,  and  keep  it  small  enough  to  prevent  injury  to  the 
generator. 

The  path  of  the  charging  current,  when  the  igniters  are  all 
open  and  the  switches  are  both  closed  in  the  up-position,  is 
(Fig.  131)  from  the  positive  brush  of  the  generator  to  5,  4,  2,  7, 

9,  12,  positive  side  of  storage  battery  and  through  the  battery, 

10,  8,  lamps  BBB,  1,3,  negative  brush  of  generator.  The  amount 
of  this  current  is  regulated  by  the  resistance  of  the  lamps,  and 
therefore  is  not  greater  than  is  safe  for  the  battery.     While  both 
switches  are   closed  in  the  down-position,  a  similar   battery- 
charging  action  occurs.     But  if  one  switch  is  closed  in  the  up- 
position  and  the  other  closed  in  the  down-position,  then   the 
generator  sends  current  through  the  battery  in  the  direction  to 


i6o  ELECTRIC  IGNITION 

discharge  it.  The  switches  should  not  be  left  closed  long  in  these 
opposite  positions. 

The  amount  and  direction  of  current  through  the  storage 
battery  while  an  igniter  is  closed  are  both  variable  in  such  a 
system  as  usually  made  up.  This  refers  to  operation  while  the 
generator  is  running  and  both  switches  are  closed  in  their  proper 
positions.  The  inductive  reaction  of  the  reactance  coil  and  the 
length  of  time  the  contact-points  of  the  igniter  are  kept  together 
both  affect  the  action  of  the  battery.  The  total  result  is  that 
the  storage  battery  is  gradually  charged  during  the  operation 
of  a  properly  designed  system.  The  storage  battery  is  thus 
kept  ready  to  supply  current  for  starting  the  engine  and  to  keep 
it  running  for  a  considerable  time. 

The  resistance  (ohmic  resistance)  of  the  reactance  coil  is  about 
one  ohm,  not  including  the  inductive  resistance. 

The  direction  of  current  through  the  igniters  can  be  reversed 
by  reversing  first  one  switch  and  then  the  other.  The  second 
switch  should  be  reversed  immediately  after  the  first.  Either 
switch  can  be  reversed  first. 

122.  Storage  Battery,  Primary  Battery,  and  i  lo-volt  Generator 
Make-and-break  System.  —  Fig.  135  is  a  diagram  of  a  system  in 
which  a  storage  battery  is  used  in  connection  with  a  generator  in 
the  manner  just  described.  A  primary  battery  is  also  included 
in  the  system  as  a  means  of  starting  the  engine  when  first  installed 
and  before  the  storage  battery  has  been  charged.  The  primary 
battery  can  also  be  used  in  an  emergency. 

The  storage  battery  is  shown  at  F  and  the  primary  battery  at 
D.  An  additional  switch  G  is  provided  for  throwing  either  the 
storage  battery  or  the  primary  battery  into  circuit.  The  switch 
is  of  the  double-pole  double- throw  type.  The  switches  are 
shown  all  three  closed  in  the  up-position  so  that  the  storage 
battery  and  generator  are  in  operation.  The  primary  battery 
is  out  of  circuit. 

To  reverse  the  current  through  the  igniters,  the  auxiliary 
switch  G  should  first  be  thrown  to  the  down-position  so  as  to 
cut  out  the  storage  battery  and  put  the  primary  battery  into 
circuit.  The  two  switches  on  the  main  board  can  then  be  re- 


MECHANICAL   MAKE-AND-BREAK  IGNITION  SYSTEMS     l6l 

versed,  one  at  a  time.  It  is  immaterial  which  of  these  two  is 
reversed  first.  The  auxiliary  switch  G  is  then  to  be  thrown  into 
its  up-position  again. 

A  6- volt  storage  battery  is  suitable  for  use  in  this  system.     The 
switchboard  is  the  same  as  that  of  Fig.  130. 


FIG.  135. 

Low-tension  Ignition  System  with  Switchboard,  Primary  Battery,  Secondary 
Battery  and  no-volt  D.  C.  Generator. 

123.  Multiple  System  with  Storage  Batteries,  i  lo-volt  Genera- 
tor, Primary  Battery,  and  Switchboards.  —  In  Fig.  136  two  units 
of  switches  and  storage  batteries,  both  the  same  as  in  the  pre- 
ceding figure,  are  connected  to  one  generator  and  one  primary 
battery.  Fuse-blocks  E  are  placed  in  the  circuit  in  the  same 
manner  and  for  the  same  purpose  as  has  been  stated  in  connection 
with  Fig.  133.  Since  the  primary  battery  is  intended  only  for 
starting  the  engine,  or  engines,  one  is  all  that  is  needed  for  both 
switchboards.  The  system  can  be  extended  to  any  number  of 
switchboards. 

The  same  precautions  must  be  observed  with  regard  to  not 
having  the  dynamo  switches  closed  in  opposite  positions  as  have 
been  pointed  out  in  connection  with  Fig.  133.  The  dynamo 
switches  are  those  at  the  right-hand  side  of  each  of  the  switch- 
boards i  and  2.  It  is  advisable  to  throw  the  auxiliary  switches  G 
up  to  the  primary  battery  position  before  reversing  the  dynamo 


162 


ELECTRIC  IGNITION 


FIG.  136. 

Two  Switchboard  Units,  Two  Storage  Batteries,  One  Primary  Battery,  and  One 
no-volt  D.  C.  Generator,  for  Supplying  Current  to  Two  Sets  of  Low-tension 
Igniters. 

switches,  and  then  throw  them  back  to  the  storage-battery  posi- 
tion after  the  reversal  has  been  made. 

124.  System  Using  Current  from  no-volt  Direct-current  Ser- 
vice without  Ground  Connection.  —  This  system,  Fig.  137, 
operates  by  charging  one  storage  battery  while  another  supplies 
current  to  the  igniters.  Neither  side  of  the  dynamo  circuit  is 
grounded  at  any  time,  therefore  the  switchboard  can  be  con- 
nected to  service  wires  such  as  supply  no- volt  direct  current 
for  general  use.  C  is  the  dynamo,  and  M  one  of  the  igniters  on 
the  engine. 

The  apparatus,  as  supplied  by  the  engine  builder,  consists  of: 

A.    Switchboard. 

BBB.  Three  no-volt  32-candle-power  carbon-filament  lamps.* 

*  If  incandescent  lamps  having  filaments  or  "pencils"  of  other  material  than 
carbon  are  used,  the  lamps  should  be  of  a  size  requiring  the  same  amount  of  cur- 
rent as  the  carbon-filament  lamps  specified.  Any  non-inductive  resistance  can 
be  used,  the  only  requirement  being  that  the  amount  of  resistance  shall  be  the 
same  as  that  of  the  lamps  specified. 


MECHANICAL   MAKE-AND-BREAK   IGNITION  SYSTEMS     163 

FF.   Two  6-volt  storage  batteries. 

D.  One  6-cell  primary  dry  battery. 

G.   One  double-pole  double-throw  4-blade  switch. 

E.  One  i5-ampere  fuse-block. 

The  connections  in  the  switchboard  A,  Fig.  137,  are  shown  in 
Fig.  138.     The  switch-blades  are  hinged  at  i,  2,  3,  and  4. 


FIG.  137. 

Switchboard  and  Low-tension  Igniter  Connections  for  Two  Storage  Batteries, 
One  Primary  Battery,  One  no-volt  Generator  and  One  Set  of  Low-tension 
Igniters. 

When  the  switches  are  closed  in  the  positions  shown  in  Fig.  137, 
the  current  to  the  igniters  comes  from  the  storage  battery  that 
is  connected  to  the  right-hand  side  of  the  switchboard.  The 
path  of  this  current  is  from  the  positive  terminal  of  that  storage 
battery  to  n  (see  Fig.  138),  and  flows  on  to  7,  3,  ground,  igniter 
M,  reactance  coil,  4,  8,  12,  and  the  negative  terminal  of  the  bat- 
tery. At  the  same  time,  the  charging  current  for  the  other 
storage  battery  comes  from  the  service  to  13  and  flows  on  to 
2,  6,  9,  auxiliary  switch  G  (Fig.  137),  positive  terminal  of  battery 


164 


ELECTRIC  IGNITION 


that  is  being  charged,  through  the  battery  to  its  negative  ter- 
minal, switch  G,  10  (Fig.  138),  5,  i,  lamps  BBB,  and  the  ter- 
minal 14,  to  which  the  negative  side  of  the  service  is  connected. 
The  charging  current  is  regulated  by  the  resistance  of  the  lamps, 
which  limit  it  to  the  amount  that  will  pass  through  them. 

When  the   4-blade  switch  is  thrown  over  to  its  right-hand 
closed  position,  the  storage  battery  connected  to  the  left-hand 


FIG.  138. 
Switchboard  Connections  for  Fig.  137. 


side  of  the  switchboard  then  furnishes  current  to  the  igniters, 
and  the  other  storage  battery  receives  charging  current  from  the 
service.  In  this  new  position  of  the  4-blade  switch,  the  cur- 
rent flows  through  the  igniters  in  the  opposite  direction  from  that 
in  which  it  did  before. 


MECHANICAL   MAKE-AND-BREAK  IGNITION  SYSTEMS     165 

The  primary  battery  is  for  starting  a  new  plant  before  either 
of  the  storage  batteries  is  charged.  It  can  of  course  be  used 
temporarily  in  case  of  emergency. 

While  this  system  has  been  referred  to  as  using  no  volts,  it 
is  satisfactorily  operative  at  any  voltage  from  no  to  125. 

125.  Multiple  System  Using  no-volt  to  i25-volt  Direct  Cur- 
rent from  General-service  Circuit.  —  This  system,  Fig.  139,  is  a 


FIG.  139. 

Two  Switchboard  Storage-battery  and  Igniter  Units  like  Fig.  137,  together  with 
One  Primary  Battery  and  One  no- volt  D.  C.  Generator. 

multiplication  of  the  switchboard,  switch,  and  storage-battery 
units  of  the  last-described  system.  Only  one  primary  battery 
is  used.  It  is  connected  to  both  switchboards. 

No  precaution  to  avoid  short-circuits  of  the  nature  mentioned 
in  connection  with  Fig.  133  is  necessary  in  this  system  since  each 
storage  battery  connected  to  the  service  for  charging  it  has  its 
own  independent  circuit  that  is  without  ground  connection,  and 
each  battery  delivering  current  to  the  igniters  has  a  circuit 
through  its  own  switchboard  only. 

126.  A  triple  low-tension  ignition  system  for  a  large  engine 
with  four  double-acting  cylinders  is  shown  in  Fig.  140.  Each 
of  the  eight  combustion  chambers  has  three  mechanically  oper- 
ated igniters.  This  is  twenty-four  igniters  for  one  engine.  The 
complete  system  for  one  engine  is  shown,  together  with  the 


i66 


ELECTRIC  IGNITION 


Rheostat 


To  No.4 
Engine 


Bus-Bar 


To  No.  3 

Engine 


Each  Engine  to  have 
Igniters,  Kick-Coils  and 
Switches  as  shown  for  No.l. 
24  Igniters  for  each 
Engine  with  four 
Double-Acting  Cylinders. 


FIG.  140. 

Connections  for  Low-tension  Ignition  System  with  Three  Igniters  in  Each  of 
Eight  Combustion  Chambers  of  One  Engine,  with  Provision  for  Extending  to 
Any  Number  of  Engines.  Two  Storage  Batteries  Operating  on  Direct  Current 
from  a  Generator. 


MECHANICAL  MAKE-AND-BREAK  IGNITION  SYSTEMS     167 

bus-bar  of  a  switchboard  and  the  switches  for  circuits  leading 
out  to  the  igniters  of  three  other  engines.  The  system  can  be 
extended  to  any  number  of  engines. 

Electric  current  is  furnished  to  the  igniters  by  storage  batteries 
only.  As  shown,  battery  A  is  connected  through  the  switch  C 
to  the  bus-bar  on  the  positive  (+)  side,  and  to  ground  on  the 
negative  (— )  side.  The  other  battery,  B,  is  connected  by  the 
switch  D  to  both  sides  of  a  charging  circuit  through  a  rheostat 
for  regulating  the  amount  of  charging  current  flowing  through 
the  battery.  C  and  D  are  both  double-pole  double-throw 
switches.  By  reversing  both  of  them,  battery  B  will  supply 
current  to  the  igniters  while  battery  A  receives  a  charge  from 
the  service  wires. 

One  side  of  each  igniter  is  grounded  to  the  metal  of  the  engine. 
The  negative  (— )  side  of  the  battery  which  is  supplying  current 
to  the  igniters  is  also  grounded  during  the  time  its  switch  is  in 
the  position  for  it  to  furnish  current  to  the  igniters.  The 
"  ground  "  is  represented  by  the  broken  line  in  the  figures. 

The  three  igniters  in  one  combustion  chamber  operate  simul- 
taneously. The  second  group  of  three  igniters  from  the  top  are 
shown  closed.  These  three  igniters  are  all  for  one  combustion 
chamber.  They  all  three  break  contact  at  the  same  instant  so 
as  to  form  three  ignition  arcs  simultaneously. 

Each  igniter  is  provided  with  its  own  individual  switch,  which 
when  open  cuts  the  igniter  and  its  kick-coil  out  of  circuit  without 
interfering  with  the  operation  of  any  other  part  of  the  ignition 
system.  One  igniter  in  each  combustion  chamber  is  fed  current 
through  one  of  the  three  switches  located  at  the  bus-bar.  The 
three  switches  for  engine  No.  i  are  at  the  right-hand  end  of  the 
bus-bar.  The  bottom  igniter  in  each  group  of  three  is  connected 
to  the  switch  at  the  extreme  right-hand  end  of  the  bus-bar. 
Opening  this  switch  cuts  out  one  igniter  in  each  of  the  combus- 
tion chambers.  The  middle  igniter  in  each  group  of  three  is 
similarly  connected  to  the  second  switch  from  the  right-hand 
end  of  the  bus-bar ;  and  the  top  igniter  of  each  group  is  connected 
to  the  remaining  switch  for  engine  No.  i  at  the  bus-bar.  Safety 
fuses  should  be  put  in  at  each  switch. 


1 68  ELECTRIC  IGNITION 

The  above  ignition  system  is  essentially  that  designed  for 
twelve  engines  of  3200  horse  power  each.  Tell-tale  kick-coils  of 
the  nature  of  that  shown  in  Fig.  123  are  used,  and  the  ignition 
apparatus  at  the  engine  is  of  the  general  nature  of  that  in  Figs. 
114  and  115.  Each  storage  battery  has  five  cells  so  as  to  give 
an  average  of  about  10  volts  while  discharging. 


CHAPTER  XIV. 

ELECTROMAGNETIC  IGNITERS  AND  IGNITION  SYSTEMS  FOR 
LOW-TENSION   CURRENT. 

127.  Principle    of    Operation.  —  In    an    electromagnetically 
operated  igniter  of  the  simplest  form,  the  contact-points  at  which 
the  arc  is  drawn  for  ignition  are  generally  kept  pressed  together 
by  a  spring  without  current  flowing  through  them  until  the 
instant  at  which  ignition  is  to  occur.     An  electromagnet  forms 
part  of  the  igniter.     As  soon  as  the  electric  circuit  is  closed,  as 
by  a  timer  which  is  a  mechanically  driven  piece  of  apparatus 
separate  from  the  igniter,  current  begins  to  flow  through  the 
magnet-coil  and  the  contact-points  of  the  igniter,  and  continues 
until  the  contact-points  are  separated  by  the  action  of  the  electro- 
magnet.    The  latter  is  energized  by  the  current  flowing  through 
it.     The  separation  of   the   contact-points  first  draws  an  arc 
suitable  for  ignition,  and  then  breaks  down  the  arc,  thus  stopping 
the  flow  of  current.     The  electromagnet  also  acts  as  a  kick-coil 
to  produce  a  suitably  hot  arc.     The  electromagnet  then  loses 
its  magnetism  and  the  contact-points  of  the  igniter  are  drawn 
together  again  by  the  action  of  the  spring  already  mentioned. 
The  different  pieces  of  apparatus  are  generally,  and  preferably, 
so  adjusted  that  the  circuit  is  broken  at  the  timer  after  the  arc 
is  broken  down  at  the  ignition-points,  and  before  the  contact- 
points  of  the  igniter  come  together  again  after  the  arc  is  broken 
down. 

128.  Elementary  Ignition  System  with  a  Timer  and  an  Igniter 
having  an  Electromagnet  with  a  Plunger  Core.  —  In  Fig.  141, 
A  is  the  stationary  contact-ring,  and  B  the  movable  contact- 
point,  between  which  the  ignition  arc  is  drawn  inside  of  the 
combustion  chamber  of  the  engine.     The  stationary  contact-ring 
A  is  rigidly  attached  to  the  rod  C  which  extends  outside  of  the 
engine  cylinder.     C  and  A  are  both  insulated  from  the  metal  of 

169 


170 


ELECTRIC  IGNITION 


the  engine.  The  movable  contact-point  B  is  carried  by  the 
rocker-arm  D,  which  is  fastened  rigidly  to  the  rod  E  that  extends 
outside  of  the  engine  cylinder  and  has  an  arm  F  rigidly  attached 
to  its  outer  end.  The  tension  spring  G  pulls  on  the  arm  F  so  as 
to  press  the  movable  contact-point  against  the  stationary  con- 


Battery    — 


Timer 


FlG.   141. 
Elementary  Low-tension  Ignition  System  with  Electrically  Operated  Igniter. 

tact-ring.  One  end  of  the  spring  is  fastened  to  some  stationary 
part  of  the  igniter.  As  represented  in  the  illustration,  the  mov- 
able rod  E  makes  metallic  (electric)  contact  with  the  metal  of 
the  engine,  and  the  arm  F  is  electrically  connected  to  the  engine 
metal  by  the  spring  G.  In  addition  to  this,  a  copper  wire  H 
connects  F  to  the  metal  of  the  engine,  the  only  purpose  of  this 
wire  being  to  insure  a  perfect  "  ground  "  connection  for  the 
movable  electrode. 

The  electromagnet  which  forms  part  of  the  igniter  is  repre- 
sented by  the  solenoid  coil  M  and  the  plunger-core  P.  The  core 
is  shown  held  partly  out  of  the  coil  by  the  tension  spring  5, 
whose  right-hand  end  is  fastened  to  some  stationary  part  of  the 
igniter.  One  end  of  the  magnet  coil  M  is  connected  at  K  to  the 
outside  end  of  the  stationary  insulated  electrode;  the  other  end 
of  the  wire  of  the  magnet  winding  is  connected  to  one  side  of 
the  battery.  The  other  side  of  the  battery  is  connected  to  the 
metallic  contact-piece  N  of  the  timer  for  closing  the  electric 
circuit  when  ignition  is  to  occur.  The  contact-piece  N  is  fast- 
ened to  a  cylindrical  piece  of  insulating  material  V  which  forms 
the  body  of  the  timer.  A  metal  arm  R  is  connected  to  a  shaft 


ELECTROMAGNETIC   IGNITERS  AND   IGNITION  SYSTEMS     171 

0  which  rotates  in  a  bearing  at  the  center  of  the  body  of  the 
timer.  R  and  0,  which  together  form  the  rotor  of  the  timer, 
are  electrically  connected  to  "  ground."  The  broken  line  indi- 
cates ground  connection. 

As  the  rotor  R  revolves,  its  outer  end  makes  electric  contact 
with  the  stationary  contact-piece  N,  thus  closing  the  electric 
circuit  through  the  igniter  once  every  revolution  of  the  timer. 
Electric  current  begins  to  flow  through  the  igniter  as  soon  as 
the  timer  closes  the  electric  circuit.  The  path  of  the  current, 
starting  from  the  positive  (+)  side  of  the  battery,  is  through  the 
coil  M  to  the  terminal  K  of  the  insulated  electrode  of  the  igniter, 
thence  through  the  contact-pieces  A  and  B  of  the  igniter,  and 
through  "  ground  "  to  the  rotor  R  of  the  timer;  from  R  the 
current  goes  to  N,  when  the  latter  two  parts  are  in  contact  with 
each  other,  and  thence  to  the  negative  (— )  side  of  the  battery. 

As  soon  as  the  current  obtains  sufficient  strength,  the  con- 
sequent energizing  of  the  magnet-coil  draws  the  plunger  P 
farther  into  the  coil  and  causes  the  tappet  U  to  strike  the  end 
of  the  arm  F  so  as  to  rotate  the  movable  electrode  slightly  and 
thus  move  the  contact-point  B  away  from  A.  This  breaks  the 
circuit  inside  the  combustion  chamber  and  draws  an  electric  arc 
for  ignition.  The  breaking  down  of  the  arc,  which  occurs  imme- 
diately after  it  is  drawn,  interrupts  the  current.  The  magnet 
coil  then  becomes  de-energized,  and  the  spring  S  draws  the 
plunger  P  back  again  to  the  position  shown.  The  spring  G  at 
the  same  time  pulls  the  contact-point  B  against  the  contact- 
ring  A  inside  the  combustion  chamber  again.  In  the  meantime 
the  rotor  R  of  the  timer  should  have  moved  out  of  contact  with 
^V.  If  R  has  not  moved  out  of  contact  with  ^V  by  the  time  the 
ignition-points  A  and  B  are  together  again  after  drawing  an  arc, 
then  the  action  of  the  igniter  will  be  immediately  repeated,  which 
is  undesirable. 

129.  Dual  Ignition  System  with  Plunger-core  Electromagnets 
in  the  Igniter.  —  Fig.  142.  The  igniters  used  in  this  system  are 
of  the  plunger-core  magnet  type  and  operate  in  the  same  general 
manner  as  the  one  shown  in  the  preceding  figure.  Each  igniter 
has  two  electromagnets;  also  two  pairs  of  contact-points  inside 


172 


ELECTRIC  IGNITION 


"Ground"on  Engine  Metal 

7T~  *^-^^— —  —  -TT  —  —  -   '  K—  —  ^~ '^~"  "**  "~  .K ~" *"— « ~^  — •-^  — •— 7T -^.^—  _ —  —  _ 


A 

A  m 

2/T 

u 

1 

la 

i 

CQ 

1 

T  — 

D.C.Generator 
FiG.  142. 

Connections  for  Low-tension  Ignition  System  with  Two  Electromagnetic  Igniters 
for  Each  of  Four  Combustion  Chambers  of  One  Engine.     The  Details 
of  the  Igniter  and  Timer  are  shown  in  Figs.  143  and  144. 


ELECTROMAGNETIC  IGNITERS  AND  IGNITION  SYSTEMS     173 

of  the  combustion  chamber.  Two  igniters  are  used  in  each  com- 
bustion chamber;  eight  igniters  for  the  four  combustion  chambers. 
Only  one  igniter  is  shown.  This  system  has  been  operated  on 
1 10- volt  current  from  a  direct-current  generator. 

The  timer  shown  has  four  brushes,  i,  2,  3,  and  4,  wEich  bear 
against  a  ring  containing  a  long  segment  /  of  insulating  material 
(vulcanized  fiber)  and  a  short  segment  H  of  metal.  The  short 
segment  H  is  electrically  connected  to  a  complete  metal  ring  F 
against  which  a  brush  E  bears.  Current  from  the  source  of 
supply  is  received  at  the  brush  E.  As  the  rings  of  the  timer 
rotate,  the  short  metal  segment  H  successively  makes  contact 
with  the  four  brushes  which  bear  against  the  ring  J-H,  thus 
causing  current  to  be  delivered  successively  to  these  four  brushes. 

When  the  timer  is  in  the  position  shown,  current  flows  from 
the  positive  (+)  brush  of  the  generator  through  the  lower  blade 
of  the  double-pole  main  switch  to  the  brush  E,  slip-ring  F,  seg- 
ment H,  brush  i,  and  thence  to  A,  where  the  current  divides, 
part  going  to  switch  Ai  and  part  to  switch  Ai.  These  two 
switches  are  for  the  two  igniters  which  are  in  one  combustion 
chamber  and  operate  simultaneously. 

The  current  from  switch  A  i  passes  through  a  safety  fuse  and 
then  divides,  part  going  to  ground  through  tell-tale  lamp  A  i  and 
the  remainder  to  igniter  Ai.  The  current  to  igniter  Ai  divides 
at  K,  part  going  through  magnet-coil  M  to  the  insulated  rod  R; 
the  other  portion  flows  through  magnet-coil  N  to  R.  The  cur- 
rent flows  through .  the  rod  R  to  the  movable  contact-points 
carried  by  the  rocker- arm  P  attached  to  R,  and  thence  to  the 
stationary  contact-points  5  and  T,  both  of  which  are  grounded 
on  the  metal  of  the  engine.  The  current  from  ground  flows 
through  the  upper  blade  of  the  main  switch  to  the  negative  (— ) 
brush  of  the  generator. 

Before  current  begins  to  flow  through  the  igniter,  the  movable 
contacts  in  the  arm  P  are  pressed  against  the  stationary  contacts 
by  action  of  the  tension  springs  W  and  X.  These  springs  pull 
the  plungers  U  and  V  partly  out  of  the  coils  until  the  movement 
of  the  plungers  is  stopped  by  the  rings  7  and  Z  striking  against 
the  arms  e  and  /  and  moving  them  back  till  the  movable  contacts 


174  ELECTRIC  IGNITION 

are  pressed  against  the  stationary  ones  in  the  combustion  cham- 
ber. As  soon  as  the  current  flowing  through  the  magnet  coils 
attains  sufficient  volume,  after  the  closing  of  the  circuit  by  the 
timer,  the  plungers  are  magnetically  drawn  into  the  coils,  thus 
causing  the  rings  g  and  h  to  strike  the  arms  e  and  /  and  separate 
the  ignition  contact-points  in  the  combustion  chamber.  The 
plungers  move  some  distance  into  the  coils  and  gain  considerable 
speed  before  the  rings  g  and  h  strike  the  arms,  thus  causing  rapid 
separation  of  the  ignition-points.  The  space  between  the  rings 
F  and  g  is  greater  than  the  thickness  of  the  arm  e,  and  the  con- 
struction of  the  upper  rings  and  arms  is  similar,  in  order  to 
obtain  this  hammer-blow  action  to  separate  the  ignition  contact 
points.  The  double-arm  member  e-f  is  insulated  from  the  elec- 
trode rod  R  by  the  insulating  ring,  or  bushing,  Q. 

The  current  from  switch  A  2  passes  through  a  safety  fuse  and 
then  divides,  part  going  to  ground  through  tell-tale  lamp  A  2  and 
the  remainder  to  igniter  A 2  (not  shown).  Igniter  A 2  is  in  the 
same  combustion  chamber  as  igniter  Ai.  Both  of  these  igniters 
operate  at  the  same  instant,  thus  drawing  two  arcs,  one  at  each 
igniter,  to  ignite  the  combustible  charge  in  one  cylinder. 

The  lamps  Ai  and  A 2  both  flash  each  time  the  timer  closes 
the  circuit  at  the  brush  i  as  shown,  during  the  rotation  of  the 
rotor  of  the  timer,  provided  the  switches  Ai  and  A 2  are  both 
closed  and  the  system  is  operating  properly.  If  one  of  the  fuses 
blows,  the  corresponding  lamp  remains  dark.  Each  of  these 
lamps  indicates  whether  current  is  going  properly  to  the  corre- 
sponding igniter.  The  movement  of  the  igniter  indicates  whether 
it  is  operating  as  it  should. 

Each  pair  of  igniters  is  connected  into  the  system  in  the  same 
manner  as  just  described  for  igniters  Ai  and  A2.  This  is  indi- 
cated by  the  lettering  on  the  diagram. 

The  lamp  G  is  for  indicating  whether  there  is  current  in  the 
main  circuit  from  the  generator.  This  lamp  glows  continuously 
while  the  pressure  in  the  main  circuit  is  correct. 

Only  one  ignition  arc  is  drawn  when  the  two  pairs  of  contact- 
points  of  one  igniter  are  separated.  This  arc  sometimes  occurs 
at  one  pair  of  ignition-points,  and  sometimes  at  the  other  pair. 


ELECTROMAGNETIC  IGNITERS  AND  IGNITION  SYSTEMS     175 

The  life  of  the  contact-points  is,  therefore,  practically  doubled 
by  the  use  of  two  pairs  of  ignition-points,  as  compared  with  only 
one  pair  for  the  same  igniter. 

The  igniter  and  timer  whose  elements  are  shown  in  the  accom- 
panying illustrations  are  shown  in  detail  in  the  following  two 
sections. 

130.  Wisconsin  Engine  Company's  Electromagnetic  Igniter 
with  Plunger  Cores.  —  Fig.  143,  five  views,  (A),  (B),  (C),  (Z>), 
and  (£).  This  igniter  has  two  pairs  of  contact-points,  of  which 
both  movable  points,  i  and  2,  are  attached  to  the  same  double- 
ended  rocker-arm  3.  The  stationary  contact-points,  4  and  5, 
are  inserted  in  lugs  6,  6,  which  project  from  the  inside  end  of 
the  body  of  the  igniter,  and  are  part  of  the  body  casting.  The 
body  of  the  igniter  fits  into  a  cylindrical  hole  which  pierces  the 
cylinder  wall  of  the  engine;  the  body  makes  a  tight  joint  near  its 
inside  end.  The  material  of  the  engine  cylinder  is  represented 
by  the  short  herring-bone  lines.  The  body  of  the  igniter  is  in 
metallic  (electric)  contact  with  the  metal  of  the  engine  cylinder. 

The  rocker-arm  3  is  carried  on  the  live  spindle  7  which  passes 
through  the  insulated  metallic  tube  8  from  end  to  end  of  the 
igniter  body;  the  tube  forms  a  bearing  for  the  spindle.  The 
tube  8  is  insulated  from  the  body  of  the  igniter  at  the  inner 
end  by  means  of  the  mica  washers  9,  and  at  the  outer  end 
by  a  wood-fiber  bushing  10.  A  nut  n  fits  on  the  outer  end 
of  the  tube  8  to  hold  the  tube  in  place.  A  coiled  compression 
spring  12  and  a  pair  of  metallic  washers  13  are  placed  between 
the  nut  ii  and  the  insulating  bushing  10.  The  expansive  force 
of  the  coiled  spring  acts  to  keep  the  flange  of  the  inner  end  of 
the  tube  8  tightly  pressed  against  the  mica  insulating  washers  9 
so  as  to  maintain  a  tight  joint  unaffected  by  different  amounts 
of  expansion  in  contiguous  parts  on  account  of  the  heat  of 
combustion. 

Two  arms,  14  and  15,  are  rigidly  attached  to  the  outside  end 
of  the  spindle  7  for  rocking  the  contact-points.  These  arms  are 
insulated  from  the  spindle  by  the  flanged  bushing  16.  The  two 
cap-screws,  one  on  each  side  of  the  spindle,  are  tightened  to  grip 
the  arms  on  the  spindle  7. 


i76 


ELECTRIC  IGNITION 


ELECTROMAGNETIC  IGNITERS  AND   IGNITION  SYSTEMS     177 

Two  solenoid  coils,  17  and  18,  each  with  a  soft-iron  or  mild- 
steel  plunger-core,  are  used  for  separating  the  contact-points  at 
which  the  arc  is  formed  for  ignition.  The  plunger-core  of  coil 
17  is  shown  by  dotted  lines  in  view  (5);  the  end  inside  of  the 
coil  is  tapered  and  bored  to  receive  one  end  of  a  non-magnetic 
rod  19,  whose  opposite  end  is  fastened  to  a  bar  20  that  forms  part 
of  a  yoke.  The  end  of  the  steel  plunger-core  that  extends  beyond 
the  end  of  the  solenoid  17  is  fastened  to  the  yoke-bar  21  by 
means  of  the  nut  22.  The  end  bars,  20  and  21,  of  the  yoke  are 
also  connected  together  outside  of  the  solenoid  by  the  rod  23, 
which  engages  with  the  forked  end  of  the  arm  14  that  is  fastened 
to  the  insulated  spindle  7  of  the  rocker-arm,  as  already  described. 
A  coiled  compression  spring  26  is  placed  between  the  yoke  end- 
bar  21  and  the  end  of  the  solenoid  coil  17.  The  expansive  force 
of  this  spring  keeps  the  collar  24  pressed  against  the  arm  14 
when  no  current  is  flowing  through  the  solenoid.  The  parts  19 
to  26  are  duplicated  in  connection  with  the  solenoid  18.  The 
action  of  the  two  springs  26  is  to  keep  the  ignition  contact-points 
pressed  together. 

When  the  ignition  timer  (not  shown)  closes  the  electric  circuit 
so  that  current  flows  through  the  two  magnet  coils  in  parallel, 
the  steel  plunger-core  of  each  solenoid  is  drawn  farther  into  the 
coil  than  when  no  current  is  flowing.  This  drawing  in  of  the 
plunger  brings  the  collar  25  against  the  side  of  the  arm  14,  and 
likewise  the  duplicate  of  collar  25  against  the  side  of  arm  15. 
This  moves  the  arms  14  and  15  so  as  to  rock  the  rocker-arm  3 
and  thus  separate  both  pairs  of  contact-points,  1-4  and  2-5.  The 
plunger-cores  move  rapidly  and  gain  considerable  speed  before 
the  collars  25  strike  the  arms  14  and  15.  Consequently  the 
collars  strike  a  hammer-blow  against  the  arms  so  as  to  cause 
rapid  separation  of  the  contact-points  at  which  the  ignition  arc 
is  to  be  formed. 

The  terminal  (binding  post)  to  which  the  wire  from  the  source 
of  electricity  is  connected  is  shown  at  27.  The  current  divides 
at  this  terminal  and  flows  through  the  two  magnet-coils  in  parallel 
and  thence  to  the  metallic  washers  13  on  the  insulated  electrode 
rod  7. 


178  ELECTRIC  IGNITION 

The  ignition  contact-points,  i,  2,  4,  and  5,  can  be  driven  out 
for  renewals  by  using  a  punch  or  piece  of  small  rod  inserted  in 
the  slightly  reduced  extension  of  the  hole  into  which  each  point 
is  fitted.  The  makers  of  this  igniter  find  that  the  use  of  two 
pairs  of  contact-points  doubles  the  life  of  the  points  as  compared 
with  an  igniter  using  only  one  pair  of  contact-points. 

The  igniter  is  constructed  for  use  on  no- volt  circuits.  The 
thickness  and  number  of  turns  of  wire  in  each  magnet-coil  of 
course  determine  the  voltage  that  is  suitable. 

131.  One-ring  Timer  for  Large  Engine  with  Four  Combustion 
Chambers.  —  The  complete  constructional  form  of  a  timer  for 
use  with  electromagnetic  igniters  is  shown  in  Fig.  144.  The 
end  view  is  shown  at  (yl),  the  side  view  at  (J3),  and  one  of  the 
brush-holders  at  (C).  The  mechanism  for  varying  the  time  of 
ignition  is  shown  in  Fig.  145  in  connection  with  the  ring,  or 
spider,  which  carries  the  brush-holders.  This  timer  embodies 
the  slip-ring  and  segmental  ring  shown  in  elementary  form  in 
Fig.  142. 

In  Fig.  144  the  current  is  brought  to  the  timer  by  the  wire  i 
connected  to  the  brush  2  which  bears  on  the  slip-ring  3.  Part 
of  the  slip-ring  3  is  broken  away  at  the  top  in  view  (A)  in  order 
to  expose  the  upper  part  of  the  long  segment  4  of  insulating 
material  and  the  side  of  the  short  metallic  segment  5,  which 
together  form  the  ring  on  which  the  four  brushes  6,  7,  8,  and  9 
bear.  The  slip-ring  3  and  the  composite  ring  4-5  are  carried  by 
the  heavy  metal  ring  10  which  fits  on  the  shaft  n.  The  slip- 
ring  3  is  broken  away  under  the  brush  2  in  view  (A)  so  that  the 
brush  apparently  bears  on  the  heavy  ring  10,  but  this  is  not 
actually  so,  since  the  brush  is  farther  forward  than  the  ring. 
The  segment  5  is  metallically  connected  to  the  slip-ring  3,  but  is 
electrically  insulated  from  all  of  the  other  parts  of  the  rotor. 

The  brush  6,  of  the  four  similar  brushes,  fits  into  the  brush- 
holder  12,  which  is  hinged  to  the  bracket  13.  This  bracket  is 
fastened  to  a  piece  of  insulating  fiber  14.  A  coiled  compression 
spring  between  the  fiber  and  the  brush  end  of  the  holder  presses 
the  brush  against  the  rotor  of  the  timer.  The  fiber  14  is  fastened 
to  a  metal  segment  15,  which  is  flanged  to  fit  into  a  circular 


ELECTROMAGNETIC   IGNITERS   AND   IGNITION   SYSTEMS 


179 


<N  bo 

"t  oj 

H  a 

«  a 

bO  £ 


o     5 


i8o 


ELECTRIC  IGNITION 


groove  in  the  ring  16.  The  ring  16  carries  all  of  the  brush-holders 
and  is  integral  with  four  arms  and  a  hub  mounted  coaxial  with 
the  rotor  of  the  timer.  The  segment  15  has  worm-wheel  teeth 
into  which  the  worm  17  meshes.  This  worm  can  be  rotated  by 
means  of  the  hand- wheel  18  on  an  extension  of  the  worm.  By 


FIG.  145. 
Ignition  Advance-and-retard  Mechanism  for  the  Timer  shown  in  Fig.  144. 

rotating  the  hand-wheel,  the  brush  is  moved  circumferentially 
around  in  the  supporting  ring  so  as  to  vary  the  time  of  ignition 
at  the  igniter,  or  igniters,  connected  to  this  brush.  The  wire 
leading  from  the  brush-holder  to  the  timer,  or  timers,  in  one 
combustion  chamber  is  connected  to  the  brush-holder  by  means 
of  the  small  screw  at  the  left-hand  end  of  the  holder.  Each  of 
the  brushes,  7,  8,  and  9  has  its  own  brush-holder,  which  is  carried 


ELECTROMAGNETIC  IGNITERS  AND   IGNITION  SYSTEMS     181 

by  the  ring  16  in  the  manner  just  described  for  brush  6,  and  is 
individually  adjustable  in  the  same  manner  for  varying  the  time 
of  ignition  of  its  igniter,  or  its  igniters. 

In  addition  to  the  individual  adjustment  of  the  brushes  as 
just  described,  all  of  the  brushes  can  be  rocked  collectively 
around  the  rotor  of  the  timer  in  order  to  simultaneously  vary 
the  time  of  ignition  in  all  of  the  combustion  chambers  of  the 
engine.  The  means  for  doing  this  are  shown  in  Fig.  145.  In 
this  figure,  the  left-hand  end  of  rod  19  is  hinged  to  the  brush- 
carrying  ring  1 6  by  the  bolt  20.  The  right-hand  end  of  the  rod 
19  is  threaded  into  the  corresponding  end  of  a  sleeve  2 1 .  Another 
rod,  22,  is  threaded  into  the  right-hand  end  of  sleeve  21,  and  the 
right-hand  end  of  this  rod  is  hinged,  by  means  of  an  end-piece, 
to  the  rocker-arm  23  by  the  T-head  bolt  24,  whose  head  fits  into 
a  slot  in  the  rocker-arm.  The  rocker-arm  is  fastened  to  the 
shaft  25,  which  is  connected  to  the  governor  of  the  engine.  The 
governor  rocks  the  shaft  25  as  the  speed  of  the  engine  varies, 
and  thus  rocks  the  brush-carrying  ring  16  so  as  to  advance  or 
retard  the  time  of  ignition  in  each  combustion  chamber  by  the 
same  amount.  The  extent  of  the  rocking  motion  given  to  the 
brush-carrying  ring  can  be  decreased  by  moving  the  bolt  24 
down  nearer  to  the  shaft  25,  or  increased  by  moving  this  bolt 
farther  away  from  the  shaft  25. 

Hand  adjustment  of  the  time  of  ignition  is  obtained  in  all  of 
the  combustion  chambers  simultaneously  by  turning  the  threaded 
sleeve  21  on  the  bolts  19  and  22.  The  sleeve  has  a  right-hand 
thread  at  one  end  and  a  left-hand  thread  at  the  other.  A  hand- 
wheel  26  is  provided  for  rotating  this  sleeve-nut.  A  lock-nut  27 
prevents  the  sleeve-nut  from  rotating  after  the  desired  setting  is 
obtained. 

132.  Allis-Chalmers  Four-ring  Timer  for  Large  Engine.  —  In 
the  photograph,  Fig.  146,  the  ring  N  near  the  front  end  of  the 
timer  rotor,  and  the  ring  P  at  the  back  part,  are  both  complete 
metallic  slip-rings.  The  segment  E  is  electrically  connected  to 
the  adjacent  front  slip-ring  N,  and  these  two  parts  are  insulated 
from  all  of  the  other  parts  of  the  rotor.  The  segment  E  forms 
part  of  a  four-segment  ring  of  which  the  other  three  metallic 


182 


ELECTRIC   IGNITION 


segments  are  two  short  segments,  one  at  each  end  of  E,  and  a 
long  segment,  one  end  of  which  is  visible  at  K.  The  long  seg- 
ment K  and  the  two  short  segments  are  insulated  from  each 
other  and  from  all  other  parts  of  the  rotor.  The  segment  F  in 
the  third  ring  from  the  front  end  of  the  rotor  is  electrically 
connected  to  the  adjacent  slip-ring  P.  Segment  F  is  like  segment 


FIG.  146.     (See  also  Figs.  147,  148,  149,  and  150.) 

Four-ring  Timers,  Switches,  and  Lamps  for  Four  Pairs  of  Electromagnetic  Igniters. 
Allis-Chalmers  Company,  Milwaukee,  Wisconsin. 

E,  and  is  part  of  a  four-piece  ring  like  that  of  which  E  is  a  seg- 
ment. F  and  P  are  together  insulated  from  the  remainder  of 
the  rotor.  In  the  ring  of  which  E  is  a  part,  the  other  three 
metallic  segments  are  electrically  insulated  from  each  other  and 
from  all  other  parts  of  the  rotor.  None  of  the  parts  which  have 
been  mentioned  has  electric  connection  with  the  metal  of  the 
engine.  The  timer  is  therefore  without  "  ground  "  connection.* 

*  In  the  diagram,  Fig.  150,  the  rings  of  the  timer  are  shown  separated  from 
each  other,  side  by  side,  together  with  the  brushes  bearing  on  them.  The  reference 
letter  is  the  same  for  any  one  part  in  both  the  photograph  and  the  diagram,  when 
the  letter  appears  in  both. 


ELECTROMAGNETIC   IGNITERS   AND   IGNITION   SYSTEMS     183 

The  assumption  of  which  is  the  positive,  and  which  the  negative 
side  of  the  supply  circuit,  as  made  below,  is  merely  for  conven- 
ience of  description. 

The  negative  side  of  the  main  switch  is  connected  to  the 
brushes  /  and  F  (shown  at  about  the  same  level  on  opposite  sides 
of  the  timer),  both  of  which  bear  on  the  slip-ring  N.  Segment 
E  is  therefore  negatively  electrified,  since  it  is  electrically  con- 
nected to  slip-ring  N. 

•  The  positive  side  of  the  main  switch  is  connected  to  the 
brushes  /  and  L  (one  at  the  top  and  the  other  at  the  bottom  of 
the  timer),  both  of  which  bear  on  the  slip-ring  P.  Segment  F 
is  connected  to  slip-ring  P,  and  is  therefore  positively  electrified. 

Brush  G  bears  on  segment  £,  and  brush  H  (next  below  G)  bears 
on  segment  F.  These  brushes  are  connected  to  the  two  double- 
pole  switches  Ai  and  A 2  on  the  switchbox  above  the  timer. 
Each  of  these  two  brushes  is  connected  to  one  blade  of  each  of 
these  two  switches.  Switch  Ai  is  connected  to  one  igniter,  and 
switch  A  2  to  the  other,  of  two  igniters  in  the  same  combustion 
chamber  of  the  engine.  These  igniters  operate  simultaneously. 

Four  brushes  bear  on  the  ring  of  which  £  is  a  segment.  The 
three  of  these  brushes  other  than  G,  all  bear  on  the  long  segment 
K  when  the  rotor  is  in  the  position  shown.  Segment  K  is 
always  electrically  dead.  The  ring  of  which  F  is  a  segment  also 
has  four  brushes  bearing  on  it,  three  of  which  are  on  the  long, 
dead  segment  as  the  rotor  is  shown.  The  pair  of  brushes,  G  and 
H,  are  the  only  ones,  of  those  on  the  segmental  rings,  that  are 
electrified  while  the  rotor  is  in  the  position  illustrated. 

As  the  rotor  revolves,  the  electrified  segments  E  and  F  first 
pass  completely  out  of  contact  with  the  brushes  G  and  H,  then 
make  contact  with  the  next  similar  pair  of  brushes,  thus  directing 
the  current  to  another  pair  of  igniters  in  another  combustion 
chamber.  The  electrified  segments  E  and  F  pass  successively 
under  all  four  of  the  brushes  that  bear  on  the  segmental  rings, 
thus  successively  directing  current  to  the  four  pairs  of  igniters 
in  the  four  combustion  chambers.  There  are  four  more  switches 
on  the  back  part  of  the  switchbox,  which  are  not  visible  in  the 
illustration.  Two  safety  fuses  are  located  under  each  switch. 


184  ELECTRIC  IGNITION 

The  two  short  segments,  one  at  each  end  of  the  electrified 
segment  E,  are  to  prevent  the  long  segment  K  from  becoming 
momentarily  electrified  each  time  the  segment  E  passes  either 
out  of  or  into  contact  with  a  brush.  While  the  segment  E  is 
passing  from  under  brush  G,  the  brush  momentarily  bridges  the 
insulation  between  G  and  the  short  segment.  The  latter  is, 
therefore,  momentarily  electrified,  since  the  brush  is  in  contact 
with  both  the  electrified  segment  E  and  the  short  segment.  The 
latter  is  long  enough  to  allow  E  to  pass  completely  out  from 
under  the  brush  before  segment  K  comes  into  contact  with  the 
brush.  The  brush  is  thus  left  dead  before  segment  K  comes 
into  contact  with  it.  The  action  is  of  the  same  general  nature 
while  segment  is  moving  into  contact  with  a  brush. 

Each  of  the  white  lamps  on  the  top  of  the  switchbox  is  con- 
nected to  one  circuit  leading  from  the  switch  to  an  igniter.  The 
lamp  is  connected  across  the  circuit  so  as  to  be  in  parallel  with 
the  corresponding  igniter.  The  lamp  flashes  each  time  the  cir- 
cuit to  the  corresponding  igniter  is  electrified.  The  red  lamp, 
in  the  midst  of  the  white  ones,  is  connected  to  the  wires  between 
the  main  switch  and  the  slip-ring  brushes  of  the  timer.  The  red 
lamp  glows  continuously  while  the  wires  going  to  the  slip-ring 
brushes  of  the  timer  are  properly  electrified;  it  remains  dark 
while  the  main  switch  is  open. 

133.  Allis-Chalmers  Electromagnetic  Igniter  for  a  Large 
Engine.  —  The  photographs,  Figs.  147  and  148,  are  from  slightly 
different  viewpoints.  The  two  views  are  shown  in  order  to 
present  the  constructive  form  as  plainly  as  possible.  Several 
parts,  which  are  completely  hidden  in  the  photographs,  are 
shown  in  the  detail  drawing,  Fig.  149.  The  essential  elements 
of  the  igniter  are  shown  in  the  skeleton  drawing  which  is  part 
of  the  wiring  diagram,  Fig.  150. 

The  reference  number  is  the  same  for  any  one  part  in  each  of 
these  figures  where  the  part  appears.  All  of  the  parts  do  not 
appear  in  all  of  the  figures. 

The  plug  i  has  a  flange  at  its  outer  end,  by  means  of  which 
it  is  fastened  to  the  engine  cylinder.  The  casing  2  incloses 
the  electromagnets  and  the  magnet-armature  which  actuate  the 


ELECTROMAGNETIC  IGNITERS  AND   IGNITION  SYSTEMS     185 


FIGS.  147,  148,  149,  and  150. 

1.  Igniter  plug,  flanged. 

2.  Housing,  or  casing,  inclosing  electromagnets  and  magnet-armature. 

3.  Shoulder  which  makes  tight  fit  (with  gasket)  in  wall  of  engine  cylinder. 

4.  Contact-piece  at  ignition  point  of  stationary  electrode  (insulated). 

5.  Rod  of  stationary  electrode  (insulated). 

6.  Arm  carrying  contact-point  of  movable  electrode  (insulated). 

7.  Outside  end  of  insulated  rod  of  movable  electrode. 

8.  Arms  rigidly  fastened  to  outside  end  of  insulated  rod  7  of  movable  electrode. 

9.  Coiled  tension  spring  for  pressing  the  outer  end  of  contact-arm  6  against  the 

stationary  contact-piece  4. 

10.  Hammer  rigidly  mounted  on  rocker-spindle  n,  whose   upper  end  extends 

through  the  top  of  housing  2. 

11.  Rocker-spindle  on  which  hammer  10  and  magnet-armature  23  (the  latter  not 

shown  in  Figs.  147  and  148)  are  rigidly  mounted. 

12.  Fiber  (insulating)  button  at  the  end  of  hammer-arm  10.     This  button  strikes 

the  arm  8  to  separate  the  contact-points  in  the  combustion  chamber. 

13.  Adjusting  screw  with  fiber  button  on  the  end.     For  preventing  hammer  10 

from  rotating  back  too  far  after  current  stops  in  the  igniter. 

14.  Tubular  bushing  (insulated)  around  the  rocker-arm  7. 

15.  Mica  washers,  or  rings,  for  insulating  stationary  electrode  4-5. 

16.  Mica  washers,  or  rings,  for  insulating  tubular  bushing  14  together  with  mov- 

able electrode  6-7. 

17.  Collar  clamped  on  rod  7  of  movable  electrode.     A  short  coiled  compression 

spring  between  this  collar  and  the  adjacent  end  of  the  tubular  bushing  14 
holds  the  hub  of  the  arm  6  against  its  seat  on  the  inside  end  of  14  so  as  to 
maintain  a  tight  joint. 

1 8.  Bolts  for  fastening  magnet-coils  in  place  in  housing  2. 

The  following  parts  are  not  visible  in  the  photographic  views. 

19.  20.   Coil  winding  of  field-magnets. 

21,  22.   Cores  and  pole-pieces  of  the  magnetic  field. 

23.  Magnet-armature.     Rigidly  attached  to  rocker-spindle  n. 


i86 


ELECTRIC  IGNITION 


igniter.     This  casing  is  bolted  to  the  flange  of  the  plug  proper. 

The  shoulder  3,  near  the  inside  end  of  the  plug,  makes  a  gas-tight 

joint,  with  the  aid  of  a  gasket,  in  the  wall  of  the  engine  cylinder. 

The  stationary  contact-piece  4  at  the  point  of  ignition  is 


,  FIG.  147.     (See  also  Figs.  148,  149,  and  150.) 

Electromagnetic  Low-tension   Igniter  with   Rocking  Magnet-Armature. 
Allis-Chalmers  Company. 

fastened  to,  or  integral  with,  the  rod  5,  which  together  form  the 
insulated  stationary  electrode  4-5.  The  outside  end  of  the  rod  5 
projects  slightly  beyond  the  nut  which  holds  the  terminal  of  the 
wire  through  which  current  is  brought  to  the  stationary  electrode. 
The  rocker-arm  6  which  carries  the  movable  contact-ignition 


ELECTROMAGNETIC   IGNITERS  AND  IGNITION   SYSTEMS     187 

point  is  fastened  to  a  rod  7  which  extends  to  the  outside  through 
an  insulated  tubular  bushing  14.  Only  a  portion  of  the  outer 
end  of  7  is  visible  in  the  photographs.  To  the  outside  end  of  7 
is  clamped  a  two-armed  piece  8,  to  the  front  arm  of  which  is 


FIG.  148. 
Another  view  of  Fig.  147. 

attached  a  coiled  tension  spring  9  for  keeping  the  ignition-contact 
points  pressed  together  when  no  current  is  flowing  through  the 
igniter.  The  rear  arm  serves  as  an  anvil  against  which  hammer 
10  strikes  so  as  to  slightly  rotate  the  electrode  6-7,  thus  causing 
separation  of  the  contact-ignition  points.  The  hammer  10  is 


i88 


ELECTRIC  IGNITION 


carried  on  a  spindle  which  extends  up  through  the  housing  2. 
A  fiber  button  12  on  the  hammer  10  strikes  the  arm  8.  This 
button  prevents  electric  connection  between  8  and  10.  The  eye- 
bolt  at  the  left-hand  end  of  the  coiled  spring  9  is  insulated  from 
the  metal  through  which  it  passes.  The  two  electrodes  are 
completely  insulated  from  the  main  body  of  the  igniter.  The 
adjusting  screw  13  prevents  the  hammer  10  from  swinging  back 
too  far.  This  screw  has  a  fiber  end  against  which  10  strikes. 
The  mica  washers  15  are  for  insulating  the  inner  end  of  the 
stationary  electrode;  and  the  mica  washers  16  are  for  insulating 


FIG.  149.     (See  also  Figs.  147,  148,  and  150.) 
Detail  of  Electromagnets  and  Hammer  of  Igniter  with  Rocking  Magnet- Armature. 

the  inner  end  of  the  tubular  bushing  14.  The  collar  17  is  clamped 
on  the  movable  electrode  rod  7,  and  has  a  coiled  compression 
spring  between  it  and  the  end  of  14  for  keeping  the  hub  of  the 
igniter  arm  6  pressed  against  the  inner  end  of  the  tube  14  so  as 
to  make  a  gas-tight  joint. 

The  magnet-coils  and  their  cores,  which  are  all  inside  of  the 
casing  2,  form,  together  with  the  iron  casing,  a  magnetic  field  of 
the  same  general  nature  as  that  of  a  bipolar  electric  generator 
of  the  more  usual  form.  These  parts  are  shown  in  Fig.  149. 
The  coils  19  and  20,  together  with  their  cores  and  pole-pieces  21 
and  22,  are  fastened  to  the  casing  2  by  the  capscrews  18  which 


ELECTROMAGNETIC  IGNITERS  AND   IGNITION   SYSTEMS     1 89 


y 

rs 

^-4-^\ 

+T^j 

+ 

1 

i  ^^+ 

E? 

5 

ir                 ll 

1             /»>j 

3  Switch       Generator 

Main  Switch 


JL 


FIG.  150.     (^ee  <i^o  Figs.  146,  147,  148,  and  149.) 

Connections  for  Four-ring  Timer  and  Eight  Electromagnetic  Igniters,  Two  in 
Each  of  Four  Combustion  Chambers  of  One  Engine. 


I QO  ELECTRIC  IGNITION 

are  threaded  into  the  magnet-cores.  A  magnet-armature  23 
of  mild  steel  is  rigidly  mounted  on  the  same  spindle  n  that 
has  the  hammer  10  rigidly  fastened  to  it.  The  magnet-arma- 
ture occupies  part  of  the  space  between  the  pole-pieces  of  the 
magnets. 

The  action  of  the  igniter  can  be  understood  by  referring  to 
its  skeleton  representation  in  Fig.  150.  The  positions  of  the 
moving  parts  there  correspond  to  those  when  no  current  is  pass- 
ing through  the  igniter.  The  movable  ignition-point  is  shown 
pressed  against  the  stationary  one  by  the  effort  of  the  coiled 
tension  spring  9.  The  hammer  10  is  rotated  back  clear  of  the 
anvil  arm  on  8.  The  magnet-armature  has  its  length  at  a  con- 
siderable angle  with  the  center  line  of  the  two  magnet-cores. 

The  path  of  the  current,  when  one  is  flowing  through  the 
igniter  from  the  positive  (+)  side  of  the  connecting  wire,  is 
through  coil  19  to  and  through  coil  20  to  the  outside  terminal  of 
the  stationary  electrode  5-4,  to  the  movable  electrode  6-7  and 
the  arm  8,  from  which  it  leaves  the  igniter  through  the  negative 
(— )  connection.  As  soon  as  a  current  starting  through  the 
igniter  gives  the  magnets  sufficient  strength,  the  armature  23  is 
rotated  by  magnetic  action,  in  the  direction  to  bring  its  length 
more  nearly  parallel  with  the  axis  of  the  magnet-cores.  The 
armature  rotates  the  spindle  n  and  the  hammer  10  with  it, 
since  they  are  all  fastened  rigidly  together.  The  hammer  strikes 
the  anvil  arm  which  is  the  rear  portion  of  8  and  moves  it  slightly 
so  as  to  rotate  the  movable  electrode  and  separate  the  ignition 
points  between  which  an  arc  is  drawn  at  the  instant  of  their 
separation.  As  soon  as  the  arc  breaks  down  and  the  current  dis- 
continues, the  tension  spring  9  draws  the  movable  electrode  back 
against  the  stationary  one  again  and  at  the  same  time  rotates 
the  hammer  10  and  magnet-armature  23  back  to  the  positions 
shown.  The  armature  is  shown  rotated  more  out  of  line  with 
the  magnet-cores  than  really  occurs,  this  being  done  in  order  to 
make  the  drawing  clear.  An  examination  of  Fig.  149  will  give 
an  idea  of  how  far  the  armature  and  hammer  rotate  back. 

Igniters  of  the  form  just  described  have  been  constructed  in 
large  sizes  for  use  on  8o-volt  current. 


ELECTROMAGNETIC  IGNITERS  AND   IGNITION  SYSTEMS     IQI 

134.  Wiring  Diagram  for  a  Four-ring  Timer  and  Igniters 
Actuated  by  a  Rotary  Magnet- Armature.  —  Fig.  150.     This  wir- 
ing diagram  is  for  a  timer  like  that  shown  in  Fig.  146,  and  for 
eight  igniters  like  that  of  Figs.  147,  148,  and  149,  two  igniters 
in  each  of  four  combustion  chambers.     The  descriptions  of  the 
timer  and  igniter  cover  practically  all  of  the  wiring  diagram 
except  the  source  of  electric  supply. 

A  generator  and  a  battery  are  represented  for  supplying  cur- 
rent to  the  system.  Either  may  be  thrown  into  circuit  by  the 
double-pole  double-throw  switch  near  the  generator.  If  a  storage 
battery  is  used,  it  must  be  charged  from  some  source  other  than 
the  generator  shown,  unless  additional  connections  are  made  for 
this  purpose.  Most  of  the  arrangements  of  generators  and  bat- 
teries which  have  been  shown  in  connection  with  mechanically 
operated  igniters  can  be  used  instead  of  the  generator  and 
battery  shown  in  the  diagram.  It  should  be  remembered,  how- 
ever, that  no  kick-coil  is  required  in  connection  with  electrically 
operated  igniters. 

135.  Igniter  with  Vibratory  Magnet- Armature.  —  The  small 
magnetic  plug  shown  in  full  view  in  Fig.  151  is  of  a  size  suitable 
for  use  on  automobile  and  small  boat  motors.     The  length  over 
all  is  slightly  less  than  4  inches,  and  the  diameter  of  the  cylin- 
drical portion  which  incloses  the  magnet-coil  is  about  IT\  inches. 
The  plug  is  shown  in  longitudinal  section  in  Fig.   152.     The 
movable  electrode,  the  magnet-core,  and  the  U-shaped  spring 
which  presses  the  movable  electrode  against  the  stationary  one, 
are  shown  in  Fig.  153. 

The  movable  contact-point  20  at  which  the  ignition  arc  is 
drawn  is  at  the  lower  end  of  the  movable  electrode  1-20,  whose 
flattened  upper  end  i  is  the  armature  of  the  magnet.  The  U-- 
shaped spring  3  presses  the  movable  electrode  against  a  blunt 
knife-edge  which  is  part  of  the  magnet-core,  or  "  pole-piece,"  2, 
and  keeps  the  movable  contact-point  20  pressed  against  the 
stationary  contact-point  21,  except  while  these  points  are  sepa- 
rated to  draw  an  ignition  arc.  The  ends  of  the  U-shaped  spring 
are  slightly  nearer  the  ignition-points  than  the  knife-edge  is. 

The  path  of  the  current  through  the  plug,  assuming  a  direction 


IQ2 


ELECTRIC  IGNITION 


of  flow  for  convenience,  is  from  the  terminal  9  through  the  plate 
10,  rivet  7,  ring  6,  magnet-coil  5,  screw  26,  body  of  the  upper 
portion  of  the  plug,  movable  electrode  1-20  to  the  stationary 
electrode  21,  which  makes  electric  connection  with  the  metal  of 
the  motor.  The  screw  26  is  one  of  the  terminals  of  the  magnet- 
coil,  and  has  metallic  contact  with  the  upper  body  of  the  plug. 
All  of  the  upper  body  of  the  plug  is  insulated  from  the  stationary 


FIGS.  151  and  152.     (See  also  Fig.  153.) 

Small   Electromagnetic  Low-tension   Igniter  Plug.     Bosch   Magneto   Company, 

New  York. 

a  =  go  millimeters.  d  =  37  millimeters. 

b  =  15  millimeters.  e  =  44.5  millimeters. 

c  =  f-inch  gas-pipe  thread. 

ignition-point  21  and  the  hexagon-head  screw-plug  23  by  means 
of  the  steatite  cone  22  and  the  mica  rings,  or  "  plates,"  18. 

As  soon  as  the  current  through  the  plug  attains  sufficient 
volume,  the  upper  end  i,  of  the  movable  electrode  1-20,  is 
attracted  toward  the  magnet-core  2.  This  causes  the  movable 
electrode  to  rock  on  the  supporting  knife-edge  and  thus  separate 
the  ignition-points  20  and  21,  so  that  an  electric  arc  is  drawn 
between  them.  The  electromagnet  acts  as  a  kick-coil  to  produce 
an  arc  suitable  for  ignition.  The  brass  piece  15  prevents  the 


ELECTROMAGNETIC  IGNITERS  AND  IGNITION  SYSTEMS     193 


upper  end  i  of  the  movable  electrode  from  being  drawn  into 
contact  with  the  steel  of  the  magnet-core,  which  action,  if  not 
prevented,  would  probably  cause  the  two  parts  to  cling  together 
longer  than  allowable  for  the  operation  of  the  igniter  at  high 
speed  of  the  motor. 


FIG.  153. 
Details  of  Magnet-Core,  Movable  Electrode,  and  Spring  of  Figs.  151  and  152. 


FIGS.  152  and  153. 


1.  Rocking  electrode. 

2.  Magnet-core  or  pole-piece. 

3.  U-shaped  spring. 

4.  Iron  sleeve. 

5.  Magnet-coil. 

6.  Current  conducting  ring. 

7.  Current  conducting  rivet. 

8.  Mica  disk. 

9.  Terminal  nut. 

10.  Current  conducting  plate. 

11.  Insulating  bush. 

12.  Mica  ring. 

13.  Upper  yoke  of  magnet. 

14.  Detachable  brass  piece. 


15.  Separating  brass  piece. 

16.  Internal  ring-nut. 

17.  Centering  ring. 

18.  Mica  rings. 

19.  Packing  ring. 

20.  Movable  ignition-point. 

21.  Stationary  ignition-point. 

22.  Steatite  insulating  cone. 

23.  Hexagon    head    with     thread 

plug. 

24.  Packing  ring  for  coil  body. 

25.  Lower  yoke  of  magnet. 

26.  Connecting  screw  at  end  of  magnet 

winding. 


of 


This  plug  should  be  operated  in  a  vertical  position,  with  the 
terminal  9  at  the  top.  The  motor  cylinder  should  be  well  cooled 
at  the  time  of  screwing  the  plug  into  it,  and  the  air-current  for 
cooling  the  motor  should  strike  the  plug.  The  upper  body  of 
the  plug  must  not  touch  the  metal  of  the  motor,  since  it  must  be 
electrically  insulated  from  the  motor  and  the  metal  of  the  car. 


194 


ELECTRIC  IGNITION 


The  plug  can  be  taken  apart  for  examination  and  cleaning  by 
unscrewing  the- coil  body  from  the  magnet-core,  or  "  pole-piece." 
The  U-shaped  spring  can  then  be  pressed  upward  by  means  of 
some  small  tool  such  as  a  screwdriver  or  knife-blade,  until  the 
crown  projects  far  enough  to  be  grasped  for  completely  remov- 
ing the  spring.  The  brass  piece  14  can  then  be  removed,  after 
which  the  removable  electrode  can  be  taken  out.  If  the  coil 
body  does  not  unscrew  readily,  kerosene  put  into  the  groove  at 
the  top  of  the  screw-plug  will  loosen  the  threads. 

136.  Magneto  and  Wiring  Diagram  for  Magnetic-plug  Igni- 
tion System.  —  Fig.  1 54  shows  the  electric  connections  between 


3  o  *>         11 

FIG.  154.     (See  also  Figs.  151,  152,  153,  155,  and  156.) 

Magnetic-plug  Ignition  System  for  Small  Motors  with  Four  Combustion  Cham 

bers.     Bosch  Magneto  Company,  New  York. 

FIGS.  154,  155,  and  156. 

1.  Permanent  field-magnets.  12.   Timing-lever. 

2.  Armature.  13.   End  cap  over  interrupter. 

3.  Flanged  tube  to  which  junction  of       14.   Spring  for  holding  end  cap. 

main  and  auxiliary  windings  is 
connected. 

4.  Fastening      screw      for      contact- 

breaker  or  interrupter. 

5.  Contact-piece  on  interrupter. 


6.  Interrupter-disk. 

7.  Long  platinum  contact-screw. 

8.  Spring  acting  on  interrupter-lever. 

9.  Short  platinum  contact-screw. 

10.  Interrupter-lever. 

11.  Segments  on  timing-lever. 


15.  Conducting  rods  on  distributer. 

16.  Carbon  brush  of  distributer. 

17.  Distributer  disk  insulation. 

18.  Connection  terminals. 

19.  Rotating  arm  of  distributer. 

20.  Dust  cover. 

21.  Fastening  nuts  for  distributer  disk. 

22.  Short-circuiting  terminal. 

23.  Connecting  piece  for  end  of  auxil- 

iary winding. 


ELECTROMAGNETIC  IGNITERS  AND   IGNITION  SYSTEMS     195 

four  magnetic  plugs  such  as  that  described  in  the  preceding 
section,  and  a  magneto  especially  adapted  to  supplying  current 
to  such  plugs.  The  plugs  are  lettered  A,  B,  C,  D.  Only  the 
parts  of  the  magneto  essential  to  showing  the  electric  connections 
appear  in  the  figure.  They  are  illustrated  in  conventional  form 
to  some  extent.  The  armature  is  shown  in  part  longitudinal  sec- 
tion at  the  middle  lower  portion  of  the  figure.  A  mechanically 
operated  interrupter  is  shown  at  the  right-hand  lower  part  of 
the  illustration,  and  just  above  it  is  a  distributer  for  directing 
the  current  to  each  of  the  igniter  plugs  in  succession.  The 
interrupter  and  distributer  are  shown  as  they  appear  when  look- 
ing toward  the  end  of  the  armature  spindle.  The  bent  inter- 
rupter-lever 10  and  the  contact-piece  5  rotate  with  the  armature. 
The  distributer  arm  19  rotates  about  a  center  which  is  concentric 
with  the  center  of  the  two  large  circles  which  surround  it.  As 
the  distributer  arm  rotates  it  makes  contact  successively  with 
the  contact-pieces  a,  6,  c,  d.  The  distributer  arm  is  shown  in 
contact  with  a  and  the  igniter  A  is  operating.  Each  of  the  heavy 
dot-and-dash  lines  is  to  show  electric  connection  either  between 
the  two  views  of  the  same  part  or  between  two  parts  which  fit 
together  so  as  to  have  electric  connection.  The  heavy  broken 
line  with  dashes  all  of  the  same  length  indicates  ground  connec- 
tion between  the  magneto  armature  and  the  ignition  plugs. 

The  magneto  armature*  is  of  the  shuttle  type  and  has  two 
windings,  one  of  which  is  a  continuation  of  the  other.  These 
windings  are  illustrated  diagrammatically  by  one  coil  of  several 
turns.  The  lower  portion  of  the  coil  may  be  called  the  main 
winding,  and  the  upper  portion  the  auxiliary  winding.  One  end 
of  the  main  winding  (the  lower  end  as  illustrated)  is  connected 
to  the  core  of  the  armature.  The  junction  point  of  the  two 
windings,  which  is  an  end  of  each  winding,  is  connected  to  the 
flange  3  of  an  insulated  tube  which  extends  through  the  hollow 
spindle  of  the  armature  and  has  the  interrupter-disk  6  fastened 
to  its  outer  end.  The  interrupter-disk  has  a  pin  which  carries 
the  interrupter-lever  10.  The  latter  has  electric  connection 

*  The  constructive  form  of  the  magneto  is  shown  in  Figs.  155  and  156.  Exam- 
ination of  these  illustrations  may  give  a  clearer  understanding  of  the  diagram. 


196  ELECTRIC  IGNITION 

with  the  disk  6  and  thence  through  the  tube  to  the  flange  3. 
The  upper  end  of  the  auxiliary  winding  is  connected  to  a  long 
screw  4  which  extends  through  the  hollow  armature  spindle  and 
the  contact-piece  5  on  the  disk  6.  The  screw  4  and  contact- 
piece  5  are  electrically  connected  together,  but  are  insulated 
from  all  other  parts  of  the  magneto  except  a  carbon  button 
(brush),  mounted  on  a  bow-spring,  and  pressed  against  the  end 
of  the  screw  4.  Electric  connection  is  made  between  the  button 


23    3   4 
FIG.  155. 

Bosch  Magneto  for  Four  Low-tension  Magnetic  Igniters.    Longitudinal  Section. 

and  the  distributer  rotor  19  by  means  of  the  clip-spring  14  and  the 
other  parts  shown  in  conjunction  with  14  in  Fig.  154.  As  the 
contact-piece  5  and  interrupter-lever  10,  both  mounted  on  the 
disk  6,  as  stated  above,  rotate  with  the  magneto  armature,  a 
piece  of  insulating  fiber  in  the  end  of  one  of  the  arms  of  the  inter- 
rupter-lever (the  right-hand  end  as  shown)  strikes  the  stationary 
segments  u,  thus  rocking  the  lever  and  causing  the  contact- 
point  at  the  left-hand  end  of  the  lever  to  move  away  from 
the  contact-piece  5.  The  contact-points  of  the  interrupter  are 


ELECTROMAGNETIC  IGNITERS  AND  IGNITION  SYSTEMS     197 

pressed  together  by  the  spring  during  the  time  the  fiber  piece 
is  not  in  contact  with  one  of  the  two  segments  n. 

While  the  electric  pressure  and  current  are  increasing  in  the 
magneto  armature  on  account  of  its  rotation  in  the  magnetic 
field,  the  contact-points  of  the  interrupter  are  kept  pressed  to- 
gether by  the  spring  8.  During  this  time  the  current  divides 
itself  between  two  electric  circuits  exterior  to  the  armature 
windings.  Part  of  the  current  flows  through  the  closed  inter- 
rupter, and  the  remainder  through  one  of  the  igniters.  The 


11 


FIG.  156. 
Interrupter  End  of  Fig.  155.     Interrupter  Cover  Removed. 

amount  of  current  through  the  igniter  during  this  time  is  not 
sufficient  to  cause  separation  of  the  ignition-points,  however. 
At,  or  about,  the  instant  the  current  through  the  interrupter 
attached  to  the  armature  spindle  attains  its  maximum  value, 
the  interrupter  circuit  is  broken  at  the  contact-points  of  the 
interrupter.  The  interrupter  is  shown  in  its  position  just  after 
its  circuit  has  been  broken  by  the  striking  of  the  piece  of  fiber 
against  the  upper  stationary  segment  n,  the  rotation  of  the 
interrupter  being  counter-clockwise  (left-hand).  The  conse- 
quent sudden  stoppage  of  the  current  flowing  through  the  inter- 


198  ELECTRIC  IGNITION 

rupter  and  auxiliary  winding  of  the  magneto  armature  causes  a 
correspondingly  sudden  increase  of  voltage  in  the  winding  of 
the  armature  and  of  current  through  the  ignition  plug.  The 
increased  current  through  the  igniter  causes  the  ignition-points 
to  separate  so  that  an  arc  is  drawn  for  ignition.  The  igniter  A 
is  shown  operating,  the  distributer  arm  being  in  contact  with 
the  corresponding  contact-piece  a  of  the  distributer. 

Two  electric  impulses  per  revolution  of  the  armature  are 
generated  in  it,  since  the  armature  is  of  the  shuttle-wound  type 
rotating  in  a  bi-polar  field.  In  order  to  deliver  current  once 
to  each  of  the  four  igniters,  the  armature  must  make  two  revo- 
lutions and  the  distributer  must  make  one  revolution.  The 
distributer  arm  is  driven  by  a  pair  of  tooth-gears,  one  on  the 
armature  spindle  and  the  other  on  the  distributer  shaft.  The 
pitch  circles  of  these  gears  are  represented  by  the  dash-and-dot 
circles  which  touch  each  other.  The  gear  on  the  igniter  shaft 
has  twice  as  many  teeth  as  the  one  on  the  armature  spindle. 
The  rotative  speed  of  the  distributer  gear  is  therefore  half  that 
of  the  armature  gear.  The  latter  is  the  driver. 

The  timing-lever  12,  to  which  are  attached  the  segments  n, 
can  be  rocked  about  the  armature  spindle  to  vary  the  time  of 
ignition  —  to  advance  or  retard  the  spark. 

The  constructive  form  of  the  magneto  with  an  interrupter  for 
operating  four  electromagnetic  igniters  is  shown  in  Figs.  155  and 
156.  The  former  is  a  longitudinal  section,  and  the  latter  is  an 
end  view  with  the  cover  cap  of  the  interrupter  removed,  the 
spring  which  holds  the  cover  cap  being  pushed  to  one  side.  The 
following  description  is  supplementary  to  that  which  has  just 
been  given.  The  cover  cap  13  has  fastened  to  it  a  bow-shaped 
spring  (not  numbered)  which  carries  a  carbon  button  (not  num- 
bered) that  presses  against  the  outer  end  of  the  screw  4.  The 
latter  is  connected  to  the  end  of  the  auxiliary  winding  of  the 
armature.  By  this  means  the  cap  13  is  placed  in  electric  con- 
nection with  the  auxiliary  winding.  The  cap  is  insulated  from 
the  contact-breaker.  The  spring  14,  which  holds  the  cap  in 
place,  connects  electrically  with  the  central  carbon  16  of  the 
distributer.  This  carbon  is  in  contact  with  the  distributer  arm 


ELECTROMAGNETIC  IGNITERS  AND  IGNITION  SYSTEMS     199 

19  and  also  with  the  terminal  22.  The  four  contact-pieces 
(a,  b,  c,  d  in  Fig.  154)  are  connected  to  the  four  terminals  18, 
one  to  each  terminal.  From  these  terminals  the  wires  lead  to 
the  igniter  plugs.  The  path  of  the  current  from  the  armature 
winding  of  the  magneto  to  the  igniter  plugs,  when  the  interrupter 
circuit  is  open,  is  through  the  screw  4,  carbon  button  and  bow- 
spring  to  the  cap  13,  thence  through  the  spring  14  and  its  fasten- 
ings to  the  central  carbon  16,  distributer  arm  19,  thence  to  one 
of  the  terminals  18  whose  contact-piece  the  distributer  touches 
at  the  moment,  to  the  igniter,  and  then  back  through  ground  to 
the  armature  of  the  magneto,  or  in  the  opposite  direction.  The 
current  flows  first  in  one  direction  and  then  in  the  opposite 
through  this  path,  since  the  magneto  produces  an  alternating 
current. 

In  order  to  have  a  convenient  means  to  cut  out  the  ignition 
while  the  magneto  is  running,  the  short-circuiting  terminal  2  2  is 
provided.  When  this  terminal  is  connected  to  ground,  as  through 
a  wire  and  switch,  the  closing  of  the  switch  diverts  the  current 
from  the  igniters  so  that  ignition  ceases. 


CHAPTER  XV. 

TRANSFORMER   SPARK-COILS  AND   SYNCHRONIZER,  OR 
MASTER,  TREMBLER-COILS. 

137.  General.  —  The  purpose  of  the  transformer  spark-coil 
in  connection  with  high-tension  ignition  is  to  transform  elec- 
tricity of  low  pressure  into  electricity  having  a  pressure  high 
enough  to  cause  it  to  jump  across  the  space  between  metallic 
parts  when  the  space  contains  a  mixture  of  air  and  fuel  in  the 
state  of  gas  or  vapor.     The  low-pressure  primary  current  which 
the  transformer  receives  rarely  has  a  pressure  greater  than  10 
volts.     The  secondary  current  which  the  transformer  delivers 
has  a  pressure  of  several  thousand  volts.     The  amount  of  elec- 
tricity decreases  during  the  transformation,  to  an  extent  some- 
what greater  proportionately  than  the  pressure  increases. 

In  order  to  cause  the  transformer  spark-coil  to  operate,  electric 
current  is  first  sent  through  it  and  then  interrupted.  The  device 
for  interrupting  the  current  is  sometimes  part  of  what  is  broadly 
known  as  the  transformer  spark-coil.  In  other  cases  the  inter- 
rupter is  separate  from  the  spark-coil,  so  far  as  mechanical 
connections  are  concerned.  The  separate  interrupter  may  be 
either  mechanically  operated,  or  it  may  be  a  coil  similar  in  a 
general  way  to  a  kick-coil  (single  winding)  provided  with  an 
electrically  operated  interrupter.  The  latter  is  generally  called 
a  master  trembler-coil,  a' master  vibrator-coil,  or  a  synchronizer 
coil. 

138.  Elementary   Transformer    Spark-Coils.  —  In  its   more 
usual  form,  the  transformer  spark-coil  consists  essentially  of  a 
core  in  the  form  of  a  bundle  or  sheaf  of  small  soft  iron  or  mild 
(soft)  steel  wires,  a  primary  winding  of  insulated  copper  wire, 
and  a  secondary  winding,  also  of  insulated  copper  wire.     There 
is  generally  a  tube  of  some  thin  strong  insulating  material  be- 
tween the  core  and  the  windings.    This  tube,  together  with 

200 


TRANSFORMER   SPARK-COILS  AND   SYNCHRONIZER        2OI 

insulating  washers,  or  rings,  at  its  ends,  forms  a  spool  for  retain- 
ing the  windings  in  place.  Some  thin  insulating  material  is 
generally  placed  between  the  two  windings  to  keep  them  sepa- 
rated from  each  other. 

The  primary  winding,  which  is  next  the  core,  consists  of  some 
200  to  300  turns  of  comparatively  thick  copper  wire  around 
which  is  wrapped  cotton  or  silk  thread  for  insulating  it.  The 
secondary  winding  consists  of  some  1500  to  2000  turns  of  thin 
copper  wire  insulated  in  the  same  manner  as  the  wire  of  the 
primary  winding.  The  secondary  winding  is  practically  always 
wound  outside  of  the  primary  winding. 

In  some  transformer  coils  all  four  of  the  ends  of  the  windings 
are  brought  out  separately;  in  others  two  of  the  wire-ends  are 


(a) 

FIG.  157. 

Four- terminal  Winding  of  Transformer  Spark- Coils.     Conventional 
Representations. 

connected  together,  an  end  of  the  primary  to  an  end  of  the  sec- 
ondary, and  only  one  wire  brought  out  from  this  junction  of  the 
two  windings.  In  the  latter  winding,  the  coil  has  only  three 
terminals,  and  the  two  windings  are  in  one  sense  continuous. 
Whether  the  two  windings  are  kept  separate  and  all  four  of  the 
wire-ends  brought  out  as  terminals,  or  the  windings  fastened 
together  end  to  end  and  only  three  terminals  brought  out,  de- 
pends chiefly  on  the  nature  of  the  ignition  system  in  which  the 
coil  is  intended  to  be  used,  as  will  appear  later. 
It  may  be  noted  that  a  transformer  coil  can  generally  be 


202 


ELECTRIC  IGNITION 


readily  distinguished  from  a  kick-coil  for  low-tension  ignition, 
by  the  difference  that  the  transformer  coil  has  either  three  or 
four  terminals,  while  the  kick-coil  has  only  two  terminals  unless 
it  is  of  unusual  design  for  some  special  purpose. 

Some  of  the  conventional  methods  of  representing  the  core 
and  windings  of  transformer  spark-coils  are  shown  in  Figs.  157 
and  158.  In  Fig.  157  the  primary  and  secondary  windings  are 
not  connected  together,  consequently  four  terminals  appear  in 
both  (a)  and  (ft),  these  being  two  conventional  methods  of  repre- 
senting this  type  of  winding.  In  (a)  the  primary  winding  is 
represented  at  the  upper  end  of  the  core,  and  the  secondary 


(a)  (b) 

FIG.  158. 

Three-terminal  Winding  of  Transformer  Spark-Coils.     Conventional 
Representations. 

winding  at  the  lower  portion.  In  (b)  the  primary  winding  is 
represented  next  to  the  core,  and  the  secondary  winding  outside 
of  the  primary.  In  Fig.  158  the  primary  and  secondary  wind- 
ings are  connected  together,  thus  leaving  only  three  terminals. 
Otherwise  these  conventional  representations  are  similar  to  those 
of  the  preceding  figure. 

139.  Operation  of  Elementary  Transformer  Spark-Coil  without 
Trembler.  —  A  plain  transformer  spark-coil  is  shown  connected 
to  an  electric  battery  in  Fig.  159.  Four  different  arrangements 
of  the  connections  are  shown,  including  the  different  locations 
of  the  break  in  the  connecting  wires.  If  in  any  of  these  arrange- 
ments the  ends  of  the  wires  are  pressed  together  at  the  break 
so  as  to  close  the  primary  circuit,  a  current  will  flow  from  the 


TRANSFORMER  SPARK-COILS  AND   SYNCHRONIZER        203 


battery  through  the  primary  winding  of  the  transformer.  Then 
by  separating  the  wire-ends  at  the  break  so  as  to  interrupt  the 
current  suddenly,  a  spark  will  be  caused  to  jump  across  the 
spark-gap  in  the  secondary  circuit.  If  the  wire-ends  were  sepa- 
rated very  slowly  so  as  to  draw  an  arc  between  them  and  thus 
cause  a  gradual  decrease  of  the  primary  current,  no  spark  would 


,Break 


Battery 


(A) 


(D) 
FIG.  159. 
Various  Connections  of  a  Transformer  Spark- Coil  and  a  Battery. 


appear  at  the  spark-gap.  Sudden  interruption  of  the  primary 
current  is  requisite  to  the  production  of  a  jump-spark.  No 
spark  appears  at  the  spark-gap  at  the  instant  of  closing  the 
primary  circuit.  This  refers  to  such  transformer  coils  as  are 
customarily  used  for  ignition  purposes,  and  when  the  primary 
current  is  not  greatly  in  excess  of  what  it  should  be.  If  an 
excessive  current  is  sent  through  the  primary  of  the  transformer, 
as  by  the  use  of  too  many  cells  in  series  in  a  battery,  it  is  possible 


204  .ELECTRIC  IGNITION 

to  produce  a  spark  sometimes  at  the  instant  of  closing  the  primary 
circuit. 

The  operation  of  the  transformer  more  in  detail  is  as  follows: 
The  current  in  the  primary  winding  magnetizes  the  iron  or  steel 
core  of  the  transformer.  Then  as  the  primary  current  ceases 
suddenly,  the  core  loses  its  magnetism  rapidly.  This  rapid 
decrease  of  magnetic  flux  through  the  core  and  also  through  the 
secondary  winding,  since  the  core  passes  through  the  secondary, 
induces  electromotive  force  in  the  secondary.  The  secondary 
circuit  being  open  at  the  spark-gap,  this  induced  electromotive 
force  builds  up  a  pressure  in  the  secondary  until  the  difference 
of  potential  between  the  two  sides  of  the  spark-gap  causes  a 
spark  to  pass  across  the  spark-gap.- 

The  circuit  of  the  high-tension  current  embraces  different 
elements,  or  combinations  of  elements,  in  the  four  arrangements 
of  Fig.  159.  The  spark-gap  is  of  course  always  included  in  the 
high-tension  circuit.  The  following  refers  to  the  high-tension 
current  that  is  induced  by  the  interruption  of  the  primary  current, 
and  which  flows  while  the  primary  circuit  is  open.  In  (A)  the 
high-tension  current  flows  through  the  secondary  winding  only; 
in  (B)  it  flows  through  the  secondary  winding  and  the  battery  in 
series;  in  (C)  through  the  secondary  and  primary  windings  in 
series;  and  in  (D)  the  secondary  current  flows  through  the  sec- 
ondary and  primary  windings  and  the  battery  in  series. 

Any  of  the  above  arrangements  of  the  spark-coil,  battery, 
and  break  in  the  primary  circuit  will  operate  satisfactorily  for 
ignition  purposes,  but  it  is  probable  that  (A)  and  (B)  are  the 
best.* 

140.  Trembler  Transformer  Spark-Coil.  —  In  Fig.  160  a 
trembler,  or  vibrator,  interrupter  and  a  condenser  are  shown  in 
connection  with  a  transformer  spark-coil  and  an  electric  battery. 
The  trembler  is  a  steel  spring  V  rigidly  fastened  at  one  end  to 
the  metal  block  A.  The  spring  has  fastened  to  it  a  contact- 
piece  M  which  is  pressed  against  a  mating  contact-piece  K  by 

*  This  last  sentence  does  not  apply  to  transformer  coils  in  which  there  is  not 
such  great  difference  in  the  number  of  turns  in  the  two  windings.  Coils  used  for 
medicinal  purposes  and  physical  treatment  are  generally  of  the  latter  class. 


TRANSFORMER  SPARK-COILS  AND   SYNCHRONIZER       205 

the  elastic  action  of  the  spring.    K  is  shown  in  the  form  of  an 
adjusting  screw  held  in  place  by  the  rigid  metal  part  B. 

The  action  of  the  trembler  is  as  follows:  Immediately  upon 
closing  the  primary  circuit,  as  by  pressing  the  wire-ends  together 
at  the  break  in  the  battery  circuit,  current  begins  to  flow  through 
the  interrupter  and  the  primary  winding  of  the  transformer  in 
series.  The  path  of  the  primary  current  is  from  the  positive 
(+)  side  of  the  battery  to  and  in  series  through  B,  K,  M,  V,  A, 
the  primary  winding  and  back  to  the  negative  (— )  side  of  the 


Condenser 


FlG.  i 60. 

Trembler  Spark-Coil  Connected  to  a  Battery  and  a  Spark-Plug.     Requires  both 
Sides  of  Timer  to  be  Insulated.     Unbroken  High-tension  Circuit. 

battery.  As  soon  as  the  transformer  core  becomes  sufficiently 
magnetized  by  the  action  of  the  current,  the  core  attracts  the 
free  end  of  the  trembler  away  from  the  stationary  contact-piece 
K,  thus  separating  M  and  K.  This  breaks  the  circuit  at  the 
trembler  contacts  and  interrupts  the  flow  of  current  through 
the  primary  winding.  As  soon  as  the  current  stops  flowing,  the 
magnet  core  loses  magnetism  to  a  sufficient  extent  to  allow 
the  end  of  the  spring  to  move  away  from  it  and  again  press  the 
contact-pieces  together.  This  closes  the  primary  circuit  so  that 


206  ELECTRIC  IGNITION 

current  begins  to  flow  through  it  again,  and  the  same  operation 
is  repeated  as  long  as  the  wire  ends  are  kept  pressed  together 
at  the  break.  A  spark  passes  at  the  spark-gap  each  time  the 
current  is  interrupted  at  the  contacts  of  the  trembler.  The 
trembler  spring  is  not  allowed  to  move  far  enough  to  touch  the 
end  of  the  magnet-core,  since  it  would  tend  to  cling  to  the  core. 
The  spring  may  be  strong  enough  to  keep  it  from  being  drawn 
against  the  core,  or  a  stop  of  some  non-magnetic  substance  such  as 
wood,  rubber,  or  brass  may  check  its  movement  toward  the  core. 

The  adjustable  contact-screw  K  affords  a  means  of  setting 
the  interrupter  so  as  to  secure  the  most  satisfactory  operation, 
and  of  taking  up  wear  at  the  contact-points  on  account  of  spark- 
ing and  burning.  This  is  the  only  adjustment  in  numerous 
makes  of  spark-coils.  Others  have  a  second  means  of  adjust- 
ment, as  will  appear  later.  Ordinarily  the  most  desirable  setting 
of  the  adjustment  means  is  that  at  which  the  least  amount  of 
current  is  required  in  connection  with  sufficiently  rapid  vibration 
of  the  trembler. 

The  condenser  prevents  excessive  sparking  and  burning  at 
the  contact-points  of  the  trembler,  and  adds  to  the  efficiency  of 
operation  of  the  transformer.  It  consists  of  numerous  sheets 
of  tin-foil  laid  together  with  thin  sheets  of  insulating  material, 
such  as  mica  or  varnished  paper,  between  them.  Each  second 
sheet  of  foil  projects  beyond  the  insulation  at  one  edge,  and 
the  remaining  (alternate)  foil  sheets  all  project  in  the  same 
manner  at  the  opposite  edge.  The  foil-sheet  edges  which  pro- 
ject next  to  each  other  are  all  pressed  together  so  as  to  make 
electric  connection  between  them,  this  set  of  sheets  forming 
what  is  called  one  side  of  the  condenser.  The  remaining  foil 
sheets,  whose  edges  project  in  the  opposite  direction,  have  their 
projecting  edges  pressed  together  in  a  similar  manner,  this  second 
set  of  sheets  forming  the  other  side  of  the  condenser.  This  dis- 
posal of  the  foil  sheets  is  shown  diagrammatically  in  the  figure, 
but  the  insulating  sheets  between  the  foil  are  not  shown.  The 
condenser  is  connected  to  A  and  B,  which  are  on  opposite  sides 
of  the  contact-points  K  and  M.  The  condenser  is  thus  placed 
in  parallel  with  the  interrupter. 


TRANSFORMER  SPARK-COILS  AND   SYNCHRONIZER       207 

During  at  least  the  first  part  of  the  separating  movement  of 
the  trembler  spring,  the  current  tends  to  keep  flowing  across  the 
gap  thus  formed  between  the  contact-points  of  the  trembler. 
If  there  is  no  condenser,  or  if  it  is  inoperative,  the  arc  drawn 
between  the  contact-points  soon  burns  and  destroys  the  contact- 
points  at  the  trembler.  But  when  the  condenser  is  operative, 
the  current,  instead  of  maintaining  an  arc  at  the  contact-points, 
is  diverted  into  the  condenser,  thus  charging  the  condenser. 
The  sparking  and  burning  at  the  contact-points  is  thus  kept 
down  to  an  amount  so  small  that  but  little  harm  is  done  to  the 
points.  The  current  ceases  to  flow  into  the  condenser  soon  after 
the  trembler  contacts  begin  to  separate,  and  the  condenser  then 
immediately  discharges  back  through  the  primary  circuit  while 
the  circuit  is  still  open  at  the  contacts.  On  account  of  the 
momentum  of  the  discharge  current,  the  condenser  immediately 
becomes  again  charged  to  a  less  extent  with  its  polarity  reversed, 
then  discharges  in  the  opposite  direction,  and  so  on  as  the  elec- 
tricity continues  oscillating.  This  oscillation  of  the  electricity 
through  the  primary  winding  produces  a  rapid  series  of  sparks 
at  the  spark-gap  in  the  secondary  circuit.  This  series  of  sparks, 
occurring  during  one  separation  of  the  trembler  contacts,  is 
ordinarily  referred  to  as  a  single  spark. 

The  current  does  not  flow  through  the  condenser. 

There  is  always  a  complete  metallic  circuit,  exclusive  of  the 
spark-gap,  for  the  high-tension  current  in  Fig.  160.  This  is  also 
true  of  Fig.  161,  which  differs  from  the  preceding  figure  in  having 
the  trembler  support  connected  to  the  junction  of  the  two  wind- 
ings instead  of  to  the  end  of  the  primary  winding. 

In  Figs.  162,  163,  164,  and  165,  which  show  different  arrange- 
ments of  the  battery  and  connections,  there  is  always  a  complete 
circuit,  exclusive  of  the  spark-gap,  for  the  secondary  current. 
This  circuit  includes  the  battery  in  each  case.  It  is  not  objec- 
tionable to  have  the  high-tension  current  flow  through  the  battery, 
however. 

All  of  the  arrangements  of  the  parts  as  shown  in  the  last  four 
figures  are  commonly  used  in  ignition  systems.  The  arrange- 
ments shown  in  Figs.  160  and  161,  although  entirely  correct  so 


208 


ELECTRIC   IGNITION 


FIG.  161. 
Same  as  Fig.  160,  Except  the  Connections  to  the  Primary  Winding  of  the  Spark-Coil. 


Condenser 


.*.  Spark 


FIG.  162. 

Trembler  Transformer  Connected  to  a  Battery  and  a  Spark-Plug  so  that  One  Side 
of  the  Timer  can  be  Grounded.     Unbroken  High-tension  Circuit. 


TRANSFORMER   SPARK-COILS  AND   SYNCHRONIZER        209 


p-n 


II 


FIG.  163. 

Trembler  Spark-Coil,  Battery  and  Spark-Plug  Connected  so  that  One  Side  of  Timer 
can  be  Grounded  and  the  Secondary  Circuit  is  Unbroken. 


FIG.  164. 
Connections  Giving  Same  Conditions  as  Stated  under  Figs.  162  and  163. 


210 


ELECTRIC  IGNITION 


far  as  the  spark-coil  and  battery  are  concerned,  are  not  so  much 
used  on  account  of  requiring  a  form  of  timer  that  is  more  expen- 
sive to  construct  than  that  which  can  be  used  with  the  four 
figures  which  follow  these  two. 

At  least  some  of  the  most  prominent  makers  of  spark-coils 
think  that  a  high-tension  trembler  spark-coil  should  not  be 
connected  to  the  other  parts  of  an  ignition  system  in  such  a 
manner  that  the  high-tension  current  must  pass  through  the 


FIG.  165. 
Connections  Giving  Same  Conditions  as  Stated  under  Figs.  162  and  163. 

trembler  contacts  of  the  spark-coil  as  a  part  of  the  only  avail- 
able high-tension  circuit  during  part  of  the  time.  Arrangements 
under  which  this  condition  may  occur  are  shown  in  Figs.  166,  167, 
1 68,  and  169.  Thus,  in  any  of  these  arrangements,  if  the  wire- 
ends  are  suddenly  separated  at  the  break  while  the  trembler  is 
operating,  the  breaking  of  the  circuit  may  occur  at  the  same 
instant  at  both  the  break  in  the  wire  and  at  the  trembler.  This 
leaves  no  metallic  circuit  for  the  high-tension  current.  The 
tendency  of  the  high-tension  current  is  then  to  jump  the  gaps 
at  the  trembler  and  at  the  break  in  the  primary  circuit.  If  the 
resistance  of  these  gaps  is  high  at  the  instant,  an  excessive  electric 
pressure  will  be  brought  to  bear  on  the  condenser  and  may  break 


TRANSFORMER   SPARK-COILS  AND   SYNCHRONIZER         211 


Condenser 


FIG.  166. 

Trembler  Spark-Coil,  Battery  and  Spark-Plug  Connected  so  that  the  High-tension 
Circuit  is  Interrupted.     One  Side  of  the  Timer  can  be  Grounded. 


FIG.  167. 
Connections  Giving  Same  Conditions  as  Stated  under  Fig.  166. 


212 


ELECTRIC  IGNITION 


FIG.  1 68. 
Connections  Giving  Same  Conditions  as  Stated  under  Fig.  166. 


FIG.  169. 
Connections  Giving  Same  Conditions  as  Stated  under  Fig.  166. 


TRANSFORMER  SPARK-COILS   AND   SYNCHRONIZER        213 

down  its  insulation.     Such  an  injury  to  the  condenser  will  of 
course  interfere  with  the  operation  of  the  spark-coil. 

141.  Safety  Spark-Gap.  —  In  order  to  protect  the  windings 
of  the  spark-coil  against  unduly  high  electric  pressure,  a  safety 
spark-gap  is  generally  used  in  connection  with  the  other  parts 
of  the  spark-coil.  Such  a  safety  gap  is  shown  in  Fig.  170.  As 
there  shown,  the  safety  gap  is  between  the  pointed  edges  of  two 
pieces  of  metal,  each  of  which  is  connected  respectively  to  an 


Condenser 


FIG.  170. 
Shows  Safety  Spark-Gap  for  Protecting  Winding  of  Spark-Coil. 

end  of  the  secondary  winding.  If  the  connections  leading  to 
the  ignition  spark-gap  are  removed,  thus  destroying  the  regular 
circuit  for  the  high-tension  current,  sparks  will  jump  across  the 
safety  gap  during  the  operation  of  the  spark-coil.  If  there  were 
no  safety  gap,  there  would  be  danger  of  the  pressure  becoming 
high  enough  to  break  down  the  insulation  of  the  transformer 
winding.  The  safety  gap  is  made  wide  enough  to  prevent  sparks 
passing  across  it  during  the  time  the  igniter  is  connected  into 
the  circuit.  Half  an  inch  or  somewhat  less  is  the  ordinary 
width  of  the  safety  gap  on  a  trembler  spark-coil.  Each  side  of 
the  gap  may  have  either  one  or  more  points.  It  is  sometimes 


214  ELECTRIC  IGNITION 

placed  inside  the  casing  which  contains  the  transformer  and 
condenser,  sometimes  outside  of  the  casing  so  as  to  be  plainly 
visible. 

142.  Lag  of  Spark-Coils.  —  Between  the  instant  of  the  closing 
of  the  primary  circuit  and  the  jumping  of  the  spark  in  the  second- 
ary circuit  (at  the  spark-plug)  of  a  trembler  spark-coil,  an  inter- 
val of  time  elapses  which  is  appreciable  in  comparison  with  the 
length  of  time  occupied  by  one  revolution  of  a  high-speed  motor, 
and  decidedly  more  appreciable  in  comparison  with  the  allow- 
able variation  in  the  time  of  ignition  as  related  to  the  position 
of  the  motor  piston  during  its  movement.     A  certain  amount  of 
time  is  required  for  the  primary  current  to  attain  its  final  strength 
in  the  primary  winding,  and  for  the  steel  core  of  the  coil  to  be- 
come sufficiently  magnetized  to  attract  the  trembler  forcibly 
enough  to  just  begin  to  move  it.     This  may  be  called  the  mag- 
netic lag  of  the  spark-coil.     Then,  after  the  magnetism  has 
become  sufficiently  strong,  more  time  is  required  to  move  the 
trembler  far  enough  to  interrupt  the  primary  current.     The 
latter  may  be  called  the  mechanical  lag  of  the  spark-coil.     It 
might  be  added  that  still  more  time  is  required  to  induce  the 
current  in  the  secondary  after  the  primary  is  interrupted,  remem- 
bering that  the  current  is  at  first  diverted  into  the  condenser, 
but  this  time  is  almost  inappreciable  in  comparison  with  that 
which  has  been  mentioned. 

143.  Tremblers,  or  Vibrators:  Bow-spring,  Hammer-break, 
and  Plain  Types.  —  In  order  to  have  satisfactory  operation  of  a 
transformer  spark-coil  with  a  trembler  interrupter,  it  is  necessary 
that  the  trembler  respond  promptly  to  the  magnetic  attraction 
of  the  magnet-core,  that  the  contact-points  separate  rapidly, 
and  that  the  contact-points  make  constant  and  firm  contact 
during  the  time  they  are  intended  to  be  pressed  together  between 
each  two  successive  vibrations  of  the  trembler.     The  prompt- 
ness of  response  to  the  magnetic  attraction  of  the  core  is  more 
especially  essential  to  satisfactory  operation  in  connection  with 
motors  which  rotate  at  high  speed.     The  above  features  are 
generally  secured  by  means  of  a  compound  trembler  of  either 
the  "  bow-spring  "  type  or  the  "  hammer-break  "  type. 


TRANSFORMER  SPARK-COILS  AND   SYNCHRONIZER        215 

A  bow-spring  trembler  is  shown  in  Fig.  171.  The  straight 
spring  V  is  rigidly  held  at  one  end  by  the  metal  block  A  to  which 
it  is  fastened  by  a  screw.  A  thin  bow-shaped  spring  W  is  fast- 
ened at  one  end  to  the  spring  V  by  means  of  rivets  near  the 


a 

D 

O-M           2 

SIS 

\ 

A 

V 

Thickness  of  Straight  Spring-  .022  Inch 
"      Bow          "      =.008     " 

FlG.  171. 

Bow-spring  Trembler  Blade  for  Spark-Coil.     The  Autocoil  Company,  136  Seventh 
Street,  Jersey  City,  New  Jersey. 

supporting  block  A.  The  bow-spring  carries  the  contact-piece 
M  at  which  the  circuit  is  broken  by  the  vibration  of  the  trembler 
during  the  operation  of  the  interrupter. 

In  the  standard  size  of  this  type  of  trembler,  the  dimensions 
are: 

Width  of  both  springs J|     inch. 

Thickness  of  straight  spring 022    " 

Thickness  of  bow-spring 008    " 

Free  length  of  straight  spring 2^  inches. 

In  a  smaller  size  of  this  trembler,  made  to  meet  conditions 
where  the  space  is  cramped,  the  free  length  of  the  flat  spring  is 
if  inches.  This  shorter  blade  is  considered  by  the  manufacturer 
as  inferior  to  the  one  of  standard  length. 

A  spark-coil  whose  interrupter  has  a  bow-spring  trembler  of 
the  above  form  is  shown  in  Figs.  172  and  173.  (The  safety 
spark-gap  appears  plainly  in  the  last  figure.) 

In  the  operation  of  the  bow-spring  trembler,  the  straight 
spring  is  first  drawn  down  a  slight  distance  by  the  attraction 
of  the  magnetized  core  of  the  spark-coil  while  the  elastic  action 


2l6 


ELECTRIC  IGNITION 


of  the  bow-spring  still  keeps  its  contact-point  pressed  against 
the  stationary  contact-piece.  The  contacts  then  separate  rapidly 
as  the  straight  spring  continues  moving  toward  the  magnetized 
core.  When  both  blades  spring  back  again  after  the  core  loses 
its  magnetism,  the  elasticity  of  the  very  thin  bow-spring  is  effec- 
tive in  keeping  the  contacts  together,  which  might  not  be  true 
if  there  were  only  one  spring  with  the  contact-point  on  it.  In 


FIG.  172. 

Trembler  Spark-Coil  with  In- 
closing Case.     Autocoil. 


FIG.  173. 

Top,  or  End,  of  Trembler  Spark-Coil  with 
Switch.     Autocoil. 


the  latter  case  the  secondary  vibrations  of  the  spring  while  the 
core  is  not  magnetized  between  successive  breaks  in  the  circuit 
have  a  tendency  to  cause  slight  (undesirable)  separations  of  the 
contact-points.  The  momentum  gained  by  the  straight  spring 
before  the  contact-points  begin  to  separate  provides  sufficient 
force  to  pull  the  contacts  apart  in  case  of  any  ordinary  amount 
of  burning  and  fusing  at  these  points.  The  bow-spring  trembler 
described  above  has  been  found  satisfactory  during  extensive 
use. 


TRANSFORMER  SPARK-COILS  AND   SYNCHRONIZER        217 

A  hammer-break  trembler  interrupter  is  shown  in  Fig.  174  in 
connection  with  the  adjacent  end  of  the  coil  box.  The  flat  steel 
blade  V  is  riveted  to  a  short  flat  spring  U  which  is  rigidly  sup- 
ported at  the  opposite  end  by  the  stationary  metal  piece  A  so  as 
to  stand  opposite  the  end  of  the  magnetic  core  E.  A  contact- 
spring  W  carries  the  movable  contact-piece  M  near  one  end  and 
is  rigidly  supported  by  A  at  the  opposite  end.  The  contact- 
spring  is  very  thin  and  flexible.  It  is  sometimes  made  of  copper. 
The  steel  trembler  carries  a  hammer  H  whose  striking  flange 


FIG.  174. 
Bogert  Hammer-break  Trembler  for  Spark-Coil,  C.  F.  Splitdorf,  New  York  City. 

stands  slightly  away  from  the  free  end  of  the  contact-spring 
when  rio  current  is  passing  through  the  spark-coil.  This  allows 
a  slight  movement  of  the  hammer  and  steel  blade  toward  the 
magnet  without  moving  the  contact-spring  and  the  attached 
contact-point  M,  further  movement  causes  the  flange  of  the 
hammer  to  strike  the  free  end  of  the  contact-spring  and  carry 
it,  together  with  the  contact-point  M,  along  during  the  remainder 
of  the  movement  toward  the  magnet,  thus  separating  the  contact- 
points.  Since  the  steel  blade  and  its  hammer  attain  considerable 
speed  before  the  hammer  strikes  the  contact-spring,  a  rapid 
separation  of  the  contact-points  is  effected.  The  hammer-blow 
is  also  effective  in  breaking  apart  the  contact-points  in  case  they 
become  stuck  together  by  fusing.  The  contact-spring,  being 
light  and  thin,  maintains  good  contact  between  the  contact-points 


2l8 


ELECTRIC  IGNITION 


while  the  hammer  is  not  touching  it.  The  movement  of  the 
hammer-blade  V  is  limited  in  both  directions  by  the  hammer- 
stop  D.  The  stationary  contact-point  K  is  in  the  end  of  an 
adjusting  screw  with  a  knurled  head  and  a  ratchet  R  against 

which  a  stop  is  pressed  by  a  spring 
so  as  to  prevent  the  screw  from  turn- 
ing of  its  own  account.  The  stop  is 
carried  by  the  stationary  part  B. 

A  spark-coil  with  a  hammer-break 
trembler  interrupter  similar  to  the 
one  just  described  is  shown  in  Fig. 
175.  The  box,  or  casing,  inclosing 
the  transformer  in  this  figure  is  of  the 
type  generally  used  for  ignition  in 

Laboratory  Type  of  Spark-Coil,     stationar      motors    Qr    for   laboratory 
Sphtdorf.  i       i  •   i 

use.     The  high-tension  terminals  are 

shown  on  the  top  of  the  box,  and  the  two  low-tension  terminals 
at  the  upper  part  of  the  front  end. 

Another  type  of  hammer-break  trembler  interrupter  is  shown 
in  Fig.  176.    The  trembler  spring  W  is  rigidly  fastened  at  its 


FIG.  175. 


FIG.  176. 

Hammer-break  Trembler  for  Spark-Coil.     Pittsfield  Spark  Coil  Company,  Dalton, 

Massachusetts. 

right-hand  end  to  the  stationary  metal  block  by  means  of  a 
screw.     The  movable  contact-piece  M  is  fastened  to  the  free 


TRANSFORMER  SPARK-COILS  AND   SYNCHRONIZER        219 

end  of  the  spring  W.  A  trembler  blade  V  is  riveted  to  the 
spring  W  at  SL  point  near  the  rigidly  supported  end  of  W.  The 
movable  contact-point  M  stands  up  through  a  hole  in  the 
trembler  blade  V  so  as  to  press  against  the  stationary  contact- 
point  K.  An  auxiliary  spring  G  presses  against  the  under  side 
of  the  trembler  spring  and  is  supported  by  a  fulcrum  F.  An 
adjusting  screw  Q  for  regulating  the  pressure  of  the  auxiliary 
spring  against  the  trembler  spring  presses  down  against  the 
right-hand  end  of  the  auxiliary  spring  G.  The  stationary  con- 
tact-point K  forms  the  point  of  an  adjustable  screw  T  which 
passes  through  the  stationary  metal  part  B.  A  lock-nut  D 
serves  to  clamp  T  firmly  in  place.  A  similar  lock-nut  R  answers 
the  same  purpose  for  the  screw  Q. 

When  no  current  is  flowing  through  the  spark-coil,  the  trembler 
spring  W  is  pressed  up  so  as  to  be  slightly  bent  and  thus  cause 
the  free  end  of  the  trembler  blade  V  to  be  separated  from  it  by 
a  slight  distance.  When  the  trembler  blade  moves  toward  the 
magnet-core  E,  the  contact-points  remain  together  during  the 
first  part  of  the  movement  of  V  until  V  strikes  the  trembler 
spring  W.  The  contact-points  are  then  rapidly  separated  on 
account  of  the  hammer-blow  thus  struck  by  V  against  W. 

A  plain  single  trembler  interrupter  is  shown  in  Fig.  177.  The 
trembler  spring  V  is  fastened  to  the  stationary  metal  block  A 


FIG.  177. 
Trembler  with  a  Single  Blade.     Splitdorf. 

by  small  screws  in  such  a  way  that  the  pressure  of  its  contact- 
point  against  the  end  of  the  contact-screw  K  can  be  regulated  by 
the  adjusting  screw  D  near  the  stationary  end  of  the  trembler 
blade.  The  contact-screw  K  is  adjustable,  but  it  is  intended 


220  ELECTRIC  IGNITION 

that  it  shall  be  adjusted  only  to  take  up  wear  at  the  contact- 
points.  The  trembler  spring  has  a  small  piece  of  soft  steel 
fastened  to  its  free  end  opposite  the  end  E  of  the  magnet-core. 
This  soft  steel  armature  is  to  cause  the  end  of  the  trembler  to  be 
more  strongly  attracted  toward  the  magnet-core  than  it  would 
be  without  the  armature. 

144.  Complete  Trembler  Transformer  Spark-Coils.  —  A  one- 
unit  spark-coil  for  stationary  or  marine  use  is  shown  in  Fig.  178. 
It  has  two  low-tension  terminals  at  the  front  end,  and  one  high- 
tension  terminal  at  the  side.  Fig.  179  is  a  one-unit  coil  intended 


FIG.  178.  FIG.  179. 

Marine  Form  of  Trembler  One-unit  Trembler  Spark-Coil  with 

Spark-Coil.  Switch.     Automobile  Type. 

for  use  on  the  dashboard  of  an  automobile.  The  high-tension 
terminal  is  at  the  bottom  of  the  box.  It  appears  large  on  account 
of  the  insulating  cap  which  covers  it.  There  is  a  switch  on  the 
front  of  the  box  by  means  of  which  either  of  two  batteries  can 
be  switched  into  circuit,  or  both  cut  out.  This  necessitates 
three  low- tension  terminals.  Two  of  these  are  at  the  bottom, 
and  the  third  at  the  top. 

A  two-unit  dash  coil  of  the  same  make  as  the  last  coil  de- 
scribed is  shown  in  Fig.  180  with  one  of  the  units  removed  from 
the  outer  casing.  The  two  high-tension  terminals  are  the  large 
ones  at  the  bottom.  The  switch  at  the  front  is  for  cutting  in 
either  of  two  batteries.  There  is  a  low- tension  terminal  at  the 


TRANSFORMER   SPARK-COILS  AND   SYNCHRONIZER         221 

top  of  each  unit,  and  two  low-tension  terminals  at  the  bottom 
of  the  box.    When  a  unit  is  placed  in  the  outer  casing,  it  auto- 


FIG.  180. 
Two-unit  Trembler  Spark-Coils  with  Switch.     Automobile  Type. 

matically  makes  the  electric  connections  necessary  to  complete 
the  circuit  inside  of  the  outer  casing.     Fig.  181  shows  a  two-unit 


FIG.  181. 

Marine  Type  of  Trembler  Spark-Coils.    Two  Units. 
Company,  Lowell,  Massachusetts. 


Heinze  Electric 


marine  or  stationary  spark-coil  with  two  high-tension  terminals 
at  the  top. 

A  four-unit  dash  coil  is  shown  in  Fig.  182.  The  switch  at 
the  front  of  the  casing  is  known  as  a  "  kick-switch/'  since  it  can 
be  operated  by  kicking  (sidewise)  the  switch  handle  at  the  lower 


222  ELECTRIC  IGNITION 

part.  When  the  small  plug  at  the  top  of  the  switch  is  removed, 
the  circuit  is  broken  so  that  it  is  impossible  to  operate  the  spark- 
coils. 


FIG.  182. 

Four  Spark-Coils  Inclosed  in  a  Case  which  has  a  Kick-Switch  and  a 
Removable  Plug. 

145.   Synchronized  Spark-Coils  with  Master  Trembler.  —  It 

is  sometimes  difficult  to  adjust  all  of  the  trembler  interrupters 
of  a  set  of  spark-coils  so  that  the  length  of  time  which  elapses 
between  the  instant  of  closing  the  primary  (low-tension)  circuit 
and  the  jumping  of  an  ignition  spark  shall  be  the  same  for  all 
coils  of  the  set.  Expressed  otherwise,  it  is  difficult  sometimes  to 
adjust  the  coils  so  that  all  of  them  shall  have  the  same  amount 
of  lag.  When  the  lag  of  the  coils  is  unequal  (in  length  of  time), 
the  ignition  sparks  do  not  jump  at  the  right  instant  in  all  of 
the  cylinders  of  the  motor.  Thus,  in  most  motors  of  the  usual 
types,  the  ignition  should  occur  at  regular  time  intervals.  It 
does  not  so  occur,  however,  if  the  .spark-coils  have  different 
amounts  of  lag. 

In  order  to  obviate  such  an  irregularity  of  lag  in  the  ignition, 
only  one  interrupter  is  sometimes  used  for  all  of  the  transformer 
spark-coils.  This  interrupter  is  caused  to  operate  by  a  single- 
wound  electromagnet  through  which  the  low-tension  current 
for  all  of  the  transformer  coils  passes.  This  single- wound  coil 


TRANSFORMER  SPARK-COILS  AND   SYNCHRONIZER         223 

and  its  interrupter  are  together  called  a  master  trembler-coil, 
a  master  vibrator-coil,  or  a  synchronizer  coil.  The  transformer 
coils  used  in  connection  with  a  synchronizer  coil  either  have  no 
interrupters,  or  their  interrupters  are  rendered  inoperative,  as  by 
screwing  down  the  contact-screw  of  each  so  that  the  contact- 
points  are  pressed  firmly  together  and  the  trembler  cannot 
vibrate,  or  by  short-circuiting  the  tremblers  with  some  electric 
conductor  such  as  a  piece  of  wire. 

A  four-unit  set  of  spark-coils  and  a  synchronizer  for  them  are 
shown  in  Fig.  183,     The  synchronizer  is  in  the  left-hand  end 


FIG.  183. 

Synchronizer  Coil  and  Four  Non-trembler  Transformer  Coils   Inclosed  in  a  Case 
which  has  a  Hand-Switch. 

of  the  outer  casing.  It  is  of  practically  the  same  shape  and  size 
externally  as  one  of  the  transformer  units.  The  connections  are 
shown  later. 

146.  Trembler  Spark-Coil  for  Use  with  High-tension  Dis- 
tributer. —  A  top  view  of  a  transformer  spark-coil  showing  the 
beginning  of  the  wires  for  connecting  it  to  the  other  parts  of  the 
ignition  system  is  shown  in  Fig.  184.  This  coil  can  be  used  for 
ignition  in  a  single-cylinder  motor  with  only  one  spark-plug, 
just  as  any  unit  coil  would  be  used  for  the  same  purpose.  But 
on  account  of  its  ability  to  do  more  work  than  is  required  for  a 
motor  with  only  one  combustion  chamber,  it  can  be  used  to 


224 


ELECTRIC  IGNITION 


transform  current  for  ignition  in  several  combustion  chambers, 
each  chamber  having  its  own  spark-plug.  This  requires  a  dis- 
tributer for  directing  the  high-tension  current  to  the  different 
spark-plugs,  as  is  explained  later.  Any  one-unit  spark-coil  can 
be  used  for  ignition  in  several  combustion  chambers  with  a  suit- 
able distributer,  provided  the  spark-coil  is  able  to  stand  up  under 


FIG.  184. 

Trembler  Spark-Coil  for  use  with  a  High-tension  Distributer  to  Direct  Current  to 
Several  Spark-Plugs  Consecutively.     Autocoil  Company. 

the  work.  Heating  and  burning  at  the  trembler  contacts  is 
one  of  the  chief  difficulties  when  a  spark-coil  is  overloaded,  as 
may  be  the  case  when  an  ordinary  coil  is  used  for  ignition  in 
several  cylinders,  as  just  mentioned. 

147.  Plain  Transformer  Spark-Coils  without  a  Trembler.  - 
Coils  of  this  nature  are  used  in  connection  with  an  interrupter 
which  is  entirely  separate  from  them.  The  interrupter  may 
be  mechanically  operated,  as  when  it  is  a  separate  piece  of 
apparatus  or  part  of  a  magneto,  or  of  a  device  for  interrupting 
the  low-tension  current  and  distributing  the  high-tension  cur- 


TRANSFORMER  SPARK-COILS  AND   SYNCHRONIZER        225 

rent,  or  it  may  be  electrically  operated,  as  when  it  is  part  of  a 
master  trembler-coil.  Plain  transformer  coils  have  long  been 
extensively  used  in  motor-cycle  ignition.  Their  use  is  becoming 
rapidly  extended  in  other  fields,  especially  that  of  the  automobile. 

A  plain  transformer  spark-coil  in  a  cylindrical  case  is  shown 
in  Fig.  185.  It  has  two  low-tension  terminals  and  one  high- 
tension  terminal. 

A  double  transformer  spark-coil  is  shown  in  Fig.  186.  Two 
separate  coils  are  inclosed  in  the  cylindrical  case.  There  are 


FIG.  185. 
Non-trembler  Transformer  Spark- Coil  in  a  Cylindrical  Case. 

five  terminals,  —  three  low- tension  and  two  high-tension  ones. 
One  of  the  low-tension  terminals  is  connected  to  both  coils. 

Fig.  187  is  a  single  transformer  coil  inclosed  in  a  wooden  box, 
which  also  contains  a  condenser.     There  are  four  terminals. 


FIG.  186.  FIG.  187. 

Two  Non-trembler  Transformers  Inclosed      Non-trembler  Transformer  with 
in  Cylindrical  Case.  Condenser  and  Terminal  Con- 

nected   to    one    side   of    the 
Condenser. 

Two  of  the  terminals  are  low-tension,  one  is  high-tension,  and 
the  remaining  one  is  for  one  side  of  the  condenser.  The  other 
side  of  the  condenser  is  connected  to  one  of  the  low-tension 
terminals. 

148.  Connections  to  Trembler  Spark-Coils.  —  Some  makers 
of  spark-coils  mark  the  terminals  of  the  coils  to  indicate  which 
terminal  is  to  be  connected  to  the  positive  side  of  the  battery, 


226  ELECTRIC  IGNITION 

etc.,  and  recommend  that  the  connections  be  made  accordingly. 
One  reason  for  this  recommendation  is  that,  when  the  connections 
are  made  as  indicated,  the  wear  on  the  contact-points  of  the 
interrupter  (trembler  contacts)  is  greater  at  the  contact-point 
which  is  the  easier  to  repair  and  the  less  expensive  to  replace 
with  another.  A  second  and  less  common  reason  is  that  better 
ignition  is  obtained  when  the  ignition  spark  jumps  in  one  direc- 
tion than  when  it  jumps  in  the  opposite  direction.  When  the 
battery  connections  are  made  as  indicated  on  the  coil,  the  igni- 
tion spark  jumps  in  the  direction  which  is  the  better  for  ignition. 


CHAPTER  XVI. 

TIMERS   AND    SPARK-PLUGS   FOR   HIGH-TENSION   IGNITION. 

Timers. 

149.  Elementary  Form  of  Timer.  —  The  device  which  periodi- 
cally closes  the  primary  (low-tension)  circuit  of  a  jump-spark 
ignition  system  at  the  proper  instant  for  ignition  is  called  a 
timer  when  it  is  a  separate  and  distinct  piece  of  apparatus.     It 
is  not  infrequently,  but  erroneously,  called  a  commutator.     A 
commutator,  as  it  appears  in  an  electric  ignition  system,  is  a 
part  of  a  direct-current  electric  generator,  or  dynamo. 

Probably  the  simplest  form  of  timer  is  a  shaft  with  a  pro- 
jecting lug  or  wire  which  strikes  a  stationary  part  as  the  shaft 
rotates,  thus  closing  the  electric  circuit  once  each  revolution  of 
the  timer  shaft.  A  timer  with  only  one  stationary  contact  will 
operate  only  one  spark-coil  when  used  in  the  ordinary  manner. 

The  rotor  of  the  timer  is  the  part,  or  parts,  which  rotate  with 
the  driving  shaft.  The  casing,  which  is  ordinarily  referred  to  as 
being  stationary,  can  be  rocked  around  the  shaft  a  quarter- 
revolution  or  less  in  order  to  advance  or  retard  the  spark;  that 
is,  to  vary  the  instant  of  ignition  relative  to  the  position  of  the 
piston  of  the  motor  during  the  movement  of  the  piston. 

150.  A  roller-contact  timer  with  four  stationary  contact-pieces, 
for  operating  four  spark-coils,  is  shown  in  Fig.  188.     It  has  a 
metal  casing  A  into  which  fits  an  insulating  ring  B,  generally  of 
wood  fiber.     Four  terminals  C,  D,  E,  F,  for  wires  leading  to  the 
spark-coils,  project  radially  from  the  casing.     The  terminal  C 
connects  with  a  contact-piece  G  whose  contact  surface  is  flush,  or 
nearly  so,  with  the  inner  surface  of  the  insulating  ring.     The 
contact-piece  and  terminal  are  insulated  from  the  metal  casing. 
In  the  same  manner,  the  terminal  D  has  the  contact-piece  H, 
and  the  other  two  terminals  have  similar  contact-pieces.     The 
rotor  K,  with  two  arms,  is  rigidly  fastened  to  a  shaft  which 

227 


228 


ELECTRIC  IGNITION 

B          A 


FIG.  188. 
Timer  for  Four  Spark-Coils.    Roller  Contact. 


!       i 


FIG.  189. 
Rolling  Contact  Timer  for  Four  Spark-Coils. 


TIMERS  AND   SPARK-PLUGS 


229 


extends  through  and  rotates  in  a  hub  that  is  part  of  the  metal 
casing.  The  bent  lever  L  is  connected  to  the  short  end  of  the 
arm  K  by  pin  M.  A  contact  roller  N  is  pinned  to  the  short 
end  of  the  bent  lever.  The  contact  roller  is  kept  pressed  against 
the  insulating  ring  and  stationary  contact-pieces  by  means  of  a 
coiled  tension  spring  P.  This  spring  pulls  the  long  end  of  the 
bent  lever  toward  the  other  rigid  arm  which  projects  to  the  left 


FIG.  190. 

Timer  with  Rubbing,  or  Sliding,  Contact.     Sectional  View. 
Spark  Coil  Company,  Dalton,  Massachusetts. 


Pittsfield 


from  K.  All  of  the  parts  inside  of  the  insulating  ring  rotate 
and  together  form  the  rotor  of  the  timer.  They  are  all  electri- 
cally connected  together. 

As  the  rotor  revolves,  the  contact  roller  makes  contact  suc- 
cessively with  the  contact-pieces  of  the  terminals,  thus  com- 
pleting the  electric  circuit  between  the  shaft  and  each  of  the 


230 


ELECTRIC  IGNITION 


terminals  in  regular  order.  The  casing  is  prevented  from  rotat- 
ing by  means  of  a  link  or  rod  connected  to  the  arm  R.  The  arm 
R  is  frequently  called  the  timing  lever. 

Another  timer  which  has  rolling  contact  is  shown  in  Fig.  189. 
The  contact  roller  N  in  this  timer  has  the  form  of  a  ring  and  is 
mounted  on  a  ball  bearing  whose  balls  run  in  a  groove  in  the  cir- 
cular part  of  Q.  The  contact  ring  N  is  kept  pressed  against  the 
inside  surface  of  the  insulating  ring  by  means  of  a  coiled  com- 
pression spring  inside  of  the  part  T. 

151.  A  sliding-contact  timer  is  illustrated  in  Fig.  190,  which  is 
a  sectional  view.     The  rotor  contact-piece  is  a  forked  spring 
which  passes  between  the  fork-shaped  ends  of  the  stationary 
contact-pieces,  thus  making  a  rubbing,  or  sliding,  contact.     The 
stationary  contact-pieces  are  insulated  from  the  metal  casing  by 
cylindrical  pieces  of  insulating  material,  one  insulator  for  each 
contact-piece. 

152.  A  timer  with  normal-pressure  contact  is  shown  in  Fig.  191. 
Two  views  are  given.     The  rotor  of  this  timer  consists  only  of  a 


FIG.  191. 

Timer  with  Plain  Pressure  Contact. 


For  Four  Spark- Coils. 


cam  whose  lobe  (protuberance)  presses  against  the  four  small 
rollers  successively  and  moves  them  outward  as  the  rotor  revolves. 
Each  of  the  four  small  rollers  is  carried  in  the  end  of  its  own 


TIMERS  AND   SPARK-PLUGS  231 

spring,  whose  opposite  end  is  rigidly  fastened  to  the  casing.  Each 
roller  spring  carries  a  small  contact-piece.  When  the  roller 
is  moved  outward  by  the  action  of  the  cam-lobe,  the  contact- 
piece  on  the  spring  presses  against  the  mating  stationary  contact- 
piece  opposite  it.  The  stationary  contact-piece  is  pressed  inward 
by  a  coiled  compression  spring  which  allows  the  contact-piece  to 
move  outward  when  the  contact-pieces  are  pressed  together. 

Spark-Plugs. 

153.  General  Description.  —  The  ordinary  form  of  high- 
tension  spark-plug  has  the  following  essential  parts:  A  hollow 
metal  piece  (bushing)  threaded  along  part  of  its  outside  for 
screwing  into  the  cylinder  of  the  motor,  and  usually  having  a 
hexagonal  head  to  be  gripped  by  a  wrench;  an  insulator  of  some 
such  material  as  porcelain,  steatite,  mica,  or  molded  compound 
which  fits  into  the  bush ;  and  a  central  wire,  rod,  or  spindle  which 
passes  through  the  insulation  from  end  to  end.  One  end  of  the 
spindle,  or  a  piece  of  metal  fastened  to  its  end,  is  either  brought 
near  to  the  end  of  the  threaded  bushing  or  to  a  piece  of  metal 
that  projects  from  the  bushing,  thus  forming  the  spark-gap  which 
goes  inside  of  the  combustion  chamber  of  the  motor.  The  outer 
end  of  the  spindle  is  provided  with  a  terminal  to  which  the  high- 
tension  wire  can  be  connected.  Packing  is  used  when  necessary, 
to  make  the  plug  gas-tight. 


FIG.  192. 
Spark-Plug  with  Insulation  Molded  into  Place. 

154.  Single-gap  Jump-spark  Plugs.  —  A  simple  form  of  plug 
is  shown  in  Fig.  192.  The  outer  bushing  i  is  insulated  from  the 
central  spindle  2  by  the  insulator  3,  which  is  molded  into  place. 


232 


ELECTRIC  IGNITION 


A  bent  wire  4  projects  from  the  bushing  so  that  the  end  of  the 
wire  is  near  the  point  of  the  insulated  spindle.  The  space  be- 
tween the  ends  of  the  spindle  and  of  the  bent  wire  is  the  spark- 
gap.  The  outer,  threaded  end  of  the  central  spindle  has  a 
ring-nut  5  and  a  thumb-nut  6  between  which  the  connecting 
wire  can  be  clamped.  The  spindle  extends  from  end  to  end  of  the 
insulation,  although  this  is  not  clearly  shown  in  the  illustration. 


FIG.  193. 
Parts  of  Spark-Plug  with  Separately  Molded  Insulation. 

The  parts  of  another  spark-plug  are  shown  separately  in 
Fig.  193.  The  threaded  outer  bushing  i  has  an  interior  shoulder 
against  which  the  packing  gasket  2  rests  when  in  place.  The 
porcelain  insulator  3  enters  the  bushing  from  the  top  and  is 
clamped  down  by  the  threaded  gland  4  so  that  the  shoulder  at 
the  under  side  of  the  ring  on  the  porcelain  presses  against  the 
gasket,  thus  making  a  gas-tight  joint.  The  hole  through  the 


TIMERS  AND   SPARK-PLUGS  233 

porcelain  is  large  at  the  bottom,  but  the  greater  portion  of  its 
length  is  small  enough  to  fit  the  spindle  5  loosely.  The  spindle 
enters  the  porcelain  from  the  bottom,  so  that  the  shoulder  on  it 
strikes  the  lower  end  of  the  small  part  of  the  hole  in  the  porcelain. 
Packing,  such  as  fiber  asbestos,  is  interposed  between  these  two 
shoulders.  The  spindle  is  drawn  tightly  into  place  by  the  ring- 
nut  6,  under  which  is  the  spring  washer  7,  whose  elasticity  allows 
for  variation  in  the  expansion  and  contraction  of  the  spindle 


SPRING  Oft  SNAP 


FIG.  194. 
Spark-Plug  with  Sheet  Mica  Insulation  and  Porcelain  Protector. 

and  the  porcelain  as  they  become  heated  and  cool.  The  usual 
terminal  thumb-nut  8  is  provided.  The  bent  wire  9  projects 
from  the  bushing  so  that  its  end  comes  within  sparking  distance 
of  the  spindle  when  the  latter  is  in  place.  The  large  hole  in  the 
lower  end  of  the  porcelain,  and  the  contracted  outer  diameter 
of  the  same  end  of  the  porcelain,  give  a  long  stretch  of  insulating 
surface  between  the  spindle  and  bushing. 

The  spark-plug  in  Fig.  194  has  mica  insulation  in  the  form  of 
a  sheet  wrapped  around  the  central  spindle.  A  protective  por- 
celain insulator  is  placed  between  the  bushing  and  the  terminal 
to  which  the  outside  wire  can  be  connected.  The  body  of  the 
spindle  is  tapered  where  it  comes  into  contact  with  the  mica  insu- 


234  ELECTRIC  IGNITION 

lation,  thus  making  the  spindle  easily  removable.  The  nut  which 
holds  the  spindle  in  place  clamps  against  the  end  of  the  porce- 
lain protector. 

155.  Spark-Plugs  with  Two  or  More  Spark-Gaps.  —  When  the 
ignition  current  is  supplied  by  a  magneto,  there  is  more  apt  to 
be  burning  away  of  the  sparking  points  of  the  spark-plug  than 
when  an  electric  battery  and  a  transformer  spark-coil  is  used. 
In  order  to  overcome  the  burning  of  the  spark-points  as  far  as 
possible,  or  at  least  to  give  the  plug  longer  life,  two  or  more  pairs 


FIG.  195. 
Spark-Plug  with  Two  Spark-Gaps.     Full  View  and  Part  Sectional  View. 

of  spark-points  are  used  in  one  plug.  The  spark  then  passes 
sometimes  between  one  pair  of  points,  and  sometimes  between 
another  pair,  thus  distributing  the  work  and  heat. 

The  spark-plug  shown  in  Fig.  195  has  two  spark-gaps  obtained 
by  bringing  two  bent  wires  from  the  outer  bushing  to  within 
sparking  distance  from  the  end  of  the  central  spindle.  The  ends 
of  the  wires  are  bent  up  so  that  if  oil  or  water  collects  on  them 
it  will  have  a  tendency  to  run  down  to  the  angle  of  the  bend 
when  the  plug  is  in  a  vertical  position,  as  shown.  The  sectional 
view  shows  how  the  plug  is  constructed.  The  insulation  between 
the  insulated  central  spindle  and  the  outer  bush  that  screws  into 
the  motor  is  of  steatite  coated  with  porcelain.  The  shoulder  of 


TIMERS  AND   SPARK-PLUGS 


235 


the  insulator  rests  on  a  packing  ring  between  it  and  the  interior 
shoulder  of  the  threaded  bush.  The  insulator  is  held  in  place 
by  a  wedge-shaped  ring  which  is  forced  into  place  and  then  held 
there  by  bending  the  top  of  the  outer  bush  inward  over  it. 


FIG.  196. 

Spark-Plug  with  Four  Spark-Gaps.    J.  S.  Bretz  Company,  Times  Building, 
New  York  City. 

In  the  spark-plug  shown  in  Fig.  196  the  insulated  central 
spindle  has  four  prongs  each  of  which  is  within  sparking  distance 


FIG.  197. 

Eisemann  Platinum  Spiral  Spark-Plug.     Eisemann-Magneto  Company,  New  York 

and  Detroit. 

from  the  outer  bush,  thus  forming  four  spark-gaps  at  which  the 
ignition  spark  may  jump. 

More  than  one  spark-gap  is  obtained  in  a  simple  manner  in 
the  plug  shown  in  Fig.  197.  The  end  of  the  outer  bush  is  bridged 
by  a  wire  around  which  is  wrapped  a  short  piece  of  thin  platinum 
wire.  The  end  of  the  insulated  central  spindle  is  flattened.  The 


236 


ELECTRIC  IGNITION 


spark  may  jump  between  the  end  of  the  spindle  and  the  nearest 
part  of  any  of  the  turns  of  the  platinum  wire. 

156.  Separable  Spark-Plugs.  —  Some  spark-plugs  are  so  con- 
structed that  they  can  readily  be  taken  apart  enough  for  clean- 
ing without  the  use  of  any  tool  for  taking  them  apart.  The 
plugs  shown  in  the  next  two  illustrations  are  of  this  nature. 


FIG.  198. 
"Breech  Block"  Separable  Spark-Plug. 

A  separable  spark-plug,  Fig.  198,  is  shown  "  open  "  in  view  (a) 
for  cleaning  or  examination.  In  view  (b)  the  plug  is  "  closed  " 
ready  for  use.  This  plug  differs  from  the  ordinary  type  in  having 
the  bushing  threaded  to  the  remainder  of  the  plug  by  a  screw 
thread,  part  of  which  is  cut  away  in  the  same  manner  as  in  the 
breech-block  of  a  cannon.  The  thread  on  each  part  is  cut  away 
in  three  places,  each  extending  about  one-sixth  of  the  way 
around  the  circumference.  This  leaves  three  sections  of  thread 


TIMERS  AND   SPARK-PLUGS 


237 


of  equal  length  on  each  part,  the  sections  being  at  equal  distances 
apart.  The  externally  threaded  part  can  be  dropped  into  the 
bushing  to  almost  the  full  distance  that  it  is  to  enter,  then  a 
twist  of  less  than  one-sixth  of  a  turn  screws  the  parts  firmly 
together.  When  the  bushing  has  been  screwed  into  the  motor, 


FIG.  199.     (See  also  next  page.) 

"Detachable"  Spark-Plug  with  Knife-edge  Spark-Gap.     Knapp-Greenwood  Com- 
pany, 1000  Boylston  Street,  Boston,  Mass. 

the  detachable  part  of  the  plug  can  be  quickly  removed  by 
twisting  it  through  less  than  one-sixth  of  a  turn  (the  flat 
handle  is  provided  for  doing  this),  then  lifting  the  detachable 
part  straight  out.  A  wire  is  shown  connected  to  the  plug  by 
means  of  a  spring  clip. 

Another  separable  plug,  Fig.  199,  is  shown  "  open  "  in  (a)  and 
"  closed  "  at  (b).    The  threaded  bushing  is  slotted,  a  portion 


238  ELECTRIC  IGNITION 

of  the  slot  being  cut  at  an  angle  like  a  screw  thread,  to  receive 
the  smooth  portion  of  the  two  screws  that  fasten  the  handle 
to  the  inner  removable  part  of  the  plug.  In  putting  the  parts 
together,  the  detachable  portion  is  dropped  into  the  bushing 
and  then  given  part  of  a  turn.  A  portion  of  the  smooth  body 
of  each  of  the  two  screws  slides  along  the  inclined  edge  of  the 


FIG.  199  —  Concluded. 

corresponding  slot,  thus  forcing  the  parts  tightly  together.  The 
parts  can  be  separated  by  the  reverse  movement. 

The  spark-gap  in  this  plug  is  the  space  between  the  edges  of 
two  hollow  cylindrical  parts.  The  lower  one  of  these  is  fastened 
to  the  insulated  central  spindle  by  the  nut  at  the  lower  end  of 
the  spindle.  The  spark  may  jump  anywhere  across  this  gap. 
The  insulation  is  built  up  of  mica  disks. 

157.  The  width  of  the  spark-gap  is  ordinarily  greater  for  an 
ignition  system  having  a  trembler  transformer  to  which  low- 
tension  current  is  supplied  by  a  battery,  than  in  a  system  operat- 
ing on  current  from  a  high-tension  magneto.  A  satisfactory 
distance  between  the  spark-points  of  an  igniter  when  the  high- 


TIMERS  AND   SPARK-PLUGS  239 

tension  current  comes  from  a  trembler  spark-coil  is  •£%  of  an  inch 
or  slightly  more.  Sometimes  as  much  as  ^  of  an  inch  is  recom- 
mended by  the  makers  of  spark-coils,  but  this  is  unusual.  For 
current  from  a  high-tension  magneto,  a  distance  from  -^  to  -fa  of 
an  inch  between  the  spark-points  appears  to  give  the  best  satis- 
faction. It  is  of  course  possible  to  construct  spark-coils  and 
magnetos  each  of  which  will  operate  most  efficiently  with  a  width 
of  spark-gap  which  is  the  same  for  all,  but  this  condition  has  not 
yet  arrived  in  general  practice. 


CHAPTER  XVII. 

JUMP-SPARK   IGNITION   SYSTEMS  WITH  MAGNETIC  TREMBLER 
INTERRUPTERS  AND   INDIVIDUAL  TRANSFORMERS. 

158.  Introductory.  —  While  the  ignition  systems  in  this  chap- 
ter are  illustrated  and  described  as  operating  on  current  from  a 
battery,  they  can  all  be  operated  with  equal  satisfaction  on 
current  from  a  direct-current  generator.  They  may  also  be 
operated  on  high-frequency  current  such  as  is  produced  by 
magnetos  with  more  than  two  magnetic  poles  of  the  type  in- 
tended for  ignition  usage,  provided  the  trembler  blade  of  the 
interrupter  is  light  enough  to  vibrate  at  a  very  high  rate. 


FIG.  200. 
High-tension  Ignition  System  with  One  Spark-Plug. 

159.   System  with  One  Spark-Plug  and  Trembler  Spark-Coil.— 

In  Fig.  200  the  spark-coil  is  shown  with  the  trembler  and  the 
two  low- tension  terminals  at  the  top,  and  the  high-tension  ter- 
minal S  at  the  side  of  the  box.  The  timer  is  represented  conven- 
tionally by  a  ring  F  of  insulating  material.  A  metal  contact- 
piece  E  is  set  into  the  insulating  ring,  and  a  rotor  R  makes  electric 

240 


JUMP-SPARK  IGNITION   SYSTEMS  241 

contact  with  the  contact-piece  E  once  during  each  revolution. 
The  rotor  of  the  timer  is  represented  as  electrically  connected  to 
the  metal  of  the  motor  by  the  broken  line  marked  "  ground." 
Two  batteries  are  shown,  either  of  which  can  be  thrown  into 
circuit  by  means  of  the  switch  whose  blade  H  can  be  swung 
around  the  pin  K  so  as  to  make  contact  with  either,  or  neither, 
of  the  two  contact-points  (switch-points)  L  and  M. 

When  the  rotor  R  of  the  timer  closes  the  battery  circuit  by 
coming  into  contact  with  E  during  its  rotation,  current  flows 
from  the  positive  side  of  the  battery  i  (as  the  switch  is  shown 
set)  through  the  switch  to  the  low-tension  terminal  P  of  the 
spark-coil,  through  the  primary  winding  of  the  spark-coil  to  the 
low-tension  terminal  T1,  thence  to  the  contact-piece  E  of  the  timer 
and  on  through  the  rotor  R  of  the  timer  to  ground,  which  takes 
it  to  the  grounded  end  of  the  wire  connected  to  the  negative  side 
of  the  battery.  The  current  completes  its  circuit  through  this, 
grounded  wire  and  the  battery  in  series. 

The  high-tension  current  flows  from  the  high-tension  terminal 
S  of  the  spark-coil  to  the  insulated  spindle  (or  firing  pin)  of  the 
spark-plug,  jumps  the  spark-gap  to  ground,  and  then  returns 
to  the  spark-coil  through  the  battery  and  switch  in  series.  Some 
of  the  high-tension  current  may  return  from  ground  to  the  battery 
through  the  timer,  but  the  portion  following  this  return  circuit 
would  be  small  under  ordinary  conditions. 

The  so-called  ground  connection  through  the  metal  of  the 
machinery  has  such  slight  electric  resistance  under  proper  con- 
ditions that  parts  which  are  connected  to  ground  can  be  con- 
sidered as  directly  connected  together. 

The  rotor  of  the  timer  is  grounded  more  or  less  perfectly  by 
the  contact  of  the  rotor  shaft  with  the  metal  of  the  bearing  in 
which  the  shaft  rotates.  Sometimes  a  brush  which  bears  on  the 
shaft  or  some  other  part  of  the  rotor,  and  is  connected  to  ground, 
is  used  to  insure  more  perfect  grounding  of  the  rotor.  If  a  timer 
with  an  insulated  rotor  is  used,  a  wire  must  be  connected  to  the 
rotor  to  carry  the  current  to  the  proper  point  outside  of  the  timer. 
This  wire  replaces  the  ground  connection  of  the  rotor  as  shown 
in  the  diagram. 


242 


ELECTRIC  IGNITION 


160.  Auxiliary  Condenser  in  an  Ignition  System.  —  In  order 
to  insure  the  occurrence  of  an  ignition  spark  even  though  the 
contacts  of  the  trembler-interrupter  should  happen  to  stick  to- 
gether, as  on  account  of  burning  and  fusing,  an  auxiliary  con- 
denser is  sometimes  used.  This  auxiliary  condenser  also  protects 
the  contact-points  of  the  timer. 

An  auxiliary  condenser  used  for  the  above  purpose  is  shown 
in  the  diagram,  Fig.  201,  which  represents  an  ignition  system 


Timer 


FIG.  201. 

Auxiliary  Condenser  in  Parallel  with  Timer  is  an  Ignition  System  with 
One  Spark-Plug. 

that  is  the  same  as  that  in  the  preceding  figure  with  an  auxiliary 
condenser  added  to  it.  The  condenser  for  protecting  the  contact- 
points  of  the  trembler  V  is  shown  at  W  connected  in  parallel 
with  the  trembler  contacts  in  the  usual  manner.  The  auxiliary 
condenser  Q  is  connected  in  parallel  with  the  timer,  one  side  of 
the  condenser  being  grounded.  The  action  of  the  auxiliary  con- 
denser relative  to  the  interruption  of  the  current  at  the  timer  is 
similar  to  that  of  the  usual  condenser  W  relative  to  interruption 
of  the  current  at  the  trembler  contacts.  The  latter  has  been 
described.  If  the  contacts  of  the  trembler  stick  together,  the 
interruption  of  the  current,  as  the  timer  points  separate  from 
each  other,  produces,  with  the  aid  of  the  condenser,  an  ignition 
spark  that  is  satisfactory  for  ignition.  Without  the  auxiliary 


JUMP-SPARK  IGNITION   SYSTEMS 


243 


condenser,  the  spark  at  the  plug  might  be  uncertain  and  weak. 
The  spark  when  the  trembler  does  not  operate  will  be  somewhat 
later  than  when  it  does,  since  the  timer  contacts  naturally  do  not 
separate  as  soon  as  the  trembler  contacts  when  the  trembler  is 
operating  properly.  The  auxiliary  condenser  may  be  either 
inside  of  the  spark-coil  box,  or  it  may  be  separate  in  a  box  of  its 
own. 

It  may  be  noted  that  if  the  auxiliary  condenser  is  not  con- 
nected to  ground,  or  is  otherwise  disconnected,  as  by  the  breaking 
of  the  connecting  wire  or  by  error,  the  system  will  then  be  the 
same  as  one  which  never  had  an  auxiliary  condenser.  No  harm 
will  be  done,  except  very  improbable  injury  to  the  timer  contacts. 


FIG.  202. 

High-tension  Ignition  System  with  One  Condenser  in  Parallel  with  Both  the 
Timer  and  the  Trembler  Interrupter.     One  Spark-Plug. 

161.  Grounded  Spark-coil  Condenser.  —  A  method  of  using 
only  one  condenser  for  both  the  trembler  of  the  spark-coil  and 
the  timer  is  shown  in  Fig.  202.  One  side  of  the  condenser  is 
connected  to  one  side  of  the  spark-coil  interrupter,  and  the  other 
side  of  the  condenser  is  grounded.  This  puts  the  condenser  in 
parallel  with  both  the  trembler  and  the  timer,  the  latter  two 
being  in  series  with  each  other.  If  the  contact-points  of  the 
trembler  separate  while  the  circuit  is  closed  at  the  timer,  the 
condenser  protects  the  trembler  contacts  and  aids  in  the  pro- 
duction of  a  good  ignition  spark  in  the  usual  manner.  If  the 
trembler  contacts  stick  together,  then  the  condenser  operates  in 


244  ELECTRIC  IGNITION 

relation  to  the  timer  when  the  contact-points  of  the  latter  sepa- 
rate, as  it  does  relative  to  the  trembler  contacts  when  they 
separate  during  the  proper  action  of  the  system. 

While  the  operation  of  this  system  is  entirely  correct  when 
all  of  the  connections  are  properly  made,  there  is  a  very  serious 
objection  to  it  for  general  application  by  those  not  familiar  with 
it.  This  objection  is  due  to  the  fact  that  most  spark-coils  for 
ignition  purposes  have  only  three  terminals,  the  condenser  hav- 
ing both  of  its  connections  to  the  other  parts  made  inside  of  the 
coil  box.  But  when  the  condenser  is  grounded,  there  must  be 
a  fourth  terminal.  The  average  operator  will  make  connections 
to  only  three  of  these,  trying  them  till  they  are  so  made  that  the 
trembler  vibrates.  This  leaves  the  condenser  out  of  action. 
The  result  is  heavy  sparking  and  rapid  burning  at  the  trembler 
contacts,  together  with  unsatisfactory  ignition  sparks  and  corre- 
spondingly bad  ignition.  The  trembler  contacts  may  be  burned 
away  so  as  to  stop  operation,  or  stick  together,  in  a  few  minutes. 
The  same  effects  are  produced  if  the  connections  are  properly 
made  at  first,  and  the  ground  connection  then  becomes  broken 
or  loose,  which  is  a  thing  that  often  happens  with  unskilled 
operators. 

In  the  hands  of  a  skilled  and  careful  operator  this  system  is 
entirely  satisfactory,  however. 

162.  Individual  Trembler-coil  System.  —  Fig.  203  represents 
a  system  with  four  trembler  spark-coils  and  the  same  number  of 
spark-plugs,  a  spark-coil  for  each  igniter  plug.  This  is  applicable 
to  a  four-cylinder  motor  of  the  single-acting  type,  or  to  a  two- 
cylinder  motor  of  the  double-acting  type. 

The  timer  in  this  case  has  four  stationary  contacts,  a,  b,  c, 
d,  spaced  at  equal  distances  around  the  insulating  ring.  Each 
of  these  contacts  is  connected  to  one  of  the  low-tension  terminals 
of  a  corresponding  spark-coil.  The  spark-coils  are  lettered  A, 
B,  C,  D,  to  correspond  to  the  lettering  of  the  stationary  contacts, 
or  terminals,  of  the  timer.  The  remaining  low-tension  terminals 
of  the  spark-coils,  one  terminal  on  each  coil,  are  connected  to  a 
main  wire  which  leads  to  the  battery  switch. 

When  the  rotor  revolves    counter-clockwise,  the  spark-coils 


JUMP-SPARK   IGNITION  SYSTEMS 


245 


are  caused  to  operate  in  the  consecutive  order  A,  B,  C,  D.  The 
connections  between  the  high-tension  terminals  of  the  spark-coils 
and  the  spark-plugs  are  made  so  that  the  sparks  jump  at  the  plugs 
in  the  consecutive  order  i,  3,  4,  2,  this  order  being  one  that  is 
usual  for  four-cylinder  motors  of  the  automobile  type.  It  is 
customary  in  such  motors  to  ignite  first  in  the  front  cylinder, 
second  in  one  of  the  middle  cylinders,  third  in  the  rear  cylinder, 


1 


Spark 


Plugs 


L 


'Ground' 


Jl-    A     TEL      A 

V  V  8P  V 

I I I I 

FIG.  203. 
Multi-coil  Ignition  System  with  Four  Spark-Plugs. 


and  fourth  in  the  remaining  middle  cylinder.  The  numerical 
order  of  ignition  might  also  be  i,  2,  4,  3,  in  accordance  with  this. 

The  timer  has  no  condenser  in  parallel  with  its  contact-points, 
consequently,  if  the  trembler  contacts  of  one  of  the  spark-coils 
stick  together,  there  will  be  no  spark  at  the  corresponding  plug, 
and  one  of  the  cylinders  will  misfire. 

163.  Synchronized  System  with  Master  Trembler-Coil.  —  In 
Fig.  204  four  transformer  spark-coils  without  interrupters,  or 
tremblers,  are  operated  on  battery  current  which  passes  through 
a  master  trembler-coil.  The  trembler  of  the  master  coil  vibrates 


246 


ELECTRIC  IGNITION 


so  as  to  rapidly  interrupt  the  current  for  each  transformer  during 
the  time  the  circuit  for  that  transformer  is  closed  by  the  timer. 
The  transformers  have  neither  tremblers  nor  condensers.  Each 
transformer  is  connected  to  its  own  spark-plug. 

While  the  battery  circuit  is  closed  for  battery  2  as  shown, 
current  flows  from  the  positive  side  of  the  battery  through  the 
switch  and  winding  of  the  master  trembler- coil  to  the  trembler 


£      FIG.  204. 
Synchronized  High-tension  Ignition  System  with  Four  Spark-Plugs. 

V,  through  the  contacts  of  the  trembler  to  the  stationary  metal 
piece  N,  thence  through  the  main  wire  F  to  the  transformer  A 
and  through  its  primary  winding  to  the  contact-piece  a  of  the 
timer,  then  through  the  rotor  of  the  timer  to  ground,  and  from 
ground  through  the  ground  wire  of  the  batteries  to  the  negative 
side  of  the  battery.  The  trembler  of.  the  master  coil  vibrates 
during  this  time,  thus  interrupting  the  current  through  the  trans- 
former so  as  to  cause  a  series  of  sparks  to  jump  between  the 
spark-points  of  the  spark-plug  i.  The  action  is  similar  for  each 


JUMP-SPARK   IGNITION   SYSTEMS  247 

of  the  other  transformers  as  the  rotor  of  the  timer  revolves  and 
closes  the  circuit  at  the  stationary  contacts  of  the  timer  in  regular 
order. 

The  condenser  /  is  in  parallel  with  the  trembler  of  the  master 
coil  and  acts  in  the  same  manner  as  when  used  in  connection 
with  a  single  transformer-coil.  This  elementary  system  has 
only  the  one  condenser. 

If  the  trembler  contacts  stick  together  or  fail  to  make  electric 
contact  with  each  other,  the  whole  ignition  system  fails  to 
operate,  or  becomes  dead,  as  a  result,  and  the  motor  stops.  The 
trembler  contacts  of  a  master  coil  used  in  this  manner  are  more 
apt  to  burn  so  as  to  fail  to  make  electric  contact  with  each  other, 
or  to  stick  together  on  account  of  fusing,  than  the  same  trembler 
used  in  connection  with  one  coil  only.  This  greater  liability  to 
trouble  is  on  account  of  the  greater  service  the  trembler  is  re- 
quired to  perform  when  used  on  a  master  coil.  In  this  particular 
system,  the  service  of  the  trembler  is  four  times  as  great  as  for 
a  single  spark-coil,  since  there  are  four  transformers  for  which 
the  trembler  must  interrupt  the  current. 

164.  Synchronized  System  with  Master  Trembler-coil  and 
Auxiliary  Condensers.  —  This  system,  shown  in  Figs.  205  and 
206,  is  the  same  as  that  of  the  preceding  figure  with  four  con- 
densers, one  for  each  transformer,  added  to  it.  There  is  also  a 
key-switch  E  inserted  in  the  circuit  of  each  transformer  —  four 
key-switches  in  all,  one  for  each  transformer.  Each  switch  is 
shown  just  above  its  transformer.  *Its  blade  is  a  flat  spring, 
something  like  that  of  the  trembler.  The  elastic  action  of  the 
spring  keeps  the  switch  closed  except  when  it  is  forced  open  by 
the  pressure  of  the  hand  or  finger  of  the  operator  on  the  button 
K.  The  purpose  of  these  key-switches  is  to  afford  a  means  of 
cutting  out  the  ignition  from  any  one  of  the  combustion  chambers 
at  will,  as  when  testing  to  discover  which  cylinder  is  misfiring, 
when  this  trouble  occurs.  The  switches  do  not  in  any  way 
affect  the  operation  of  the  system  while  the  motor  is  running  in 
the  ordinary  manner. 

Each  of  the  auxiliary  condensers  has  one  side  grounded,  all  of 
them  being  grounded  through  one  main  wire.  The  condenser  Q 


248 


ELECTRIC  IGNITION 


has  the  other  side  connected  to  the  stationary  block  E  of  the  key- 
switch  just  above  the  transformer  A.  This  is  practically  the 
same,  so  far  as  the  operation  of  the  condenser  is  concerned,  as 
if  the  condenser  were  connected  to  the  stationary  contact  a  of 
the  timer,  since  there  is  no  transformer  winding,  or  other  in- 
ductive resistance,  between  the  switch  and  timer.  The  con- 


FIG.  205. 

Synchronized  Ignition  System  with  a  Grounded  Condenser  in  Parallel  with  Each 
Transformer  Spark-Coil. 

denser  Q  is  therefore  in  parallel  with  the  timer.  The  other  three 
auxiliary  condensers  are  similarly  connected  relative  to  the 
transformers  B,  C,  and  D  respectively. 

If  the  trembler  contacts  (of  the  master  coil  M)  stick  together 
so  that  the  trembler  does  not  interrupt  the  current,  then  the 
auxiliary  condensers  will  act  so  that  when  the  timer  circuit  is 
broken  by  the  separation  of  the  timer  rotor  from  any  one  of  its 
stationary  contacts,  a  spark  suitable  for  ignition  will  jump  between 
the  points  of  the  corresponding  spark-plug.  This  would  probably 
not  occur  if  there  were  no  auxiliary  condenser,  or  if  a  spark  did 
jump  it  would  not  be  as  strong  as  when  there  is  a  condenser  in 


JUMP-SPARK  IGNITION   SYSTEMS 


249 


parallel  with  the  timer.     The  condenser  also  protects  the  con- 
tact-points of  the  timer,  which  would  suffer  during  the  time  the 


Timer 


Extra  Ground  Wire 
Engine 

FiG.  206. 
Constructive  Form  of  Fig.  205.     C.  F.  Splitdorf,  New  York  City. 

trembler  contacts  are  stuck  together,  if  the  auxiliary  condensers 
were  not  in  the  system. 

165.  Ammeter  and  Voltmeter  Permanently  in  the  Circuit  of  a 
High-tension  Ignition  System.  —  Fig.  207.  The  ammeter  and 
voltmeter  are  mounted  on  the  same  base,  and  the  upper  terminal 
(marked  — )  is  in  connection  with  both  instruments.  The  volt- 
meter terminal  (marked  +)  is  at  the  right-hand  side,  and  the 
ammeter  terminal  at  the  left-hand  side. 

The  upper  terminal,  common  to  both  the  ammeter  and  volt- 
meter, is  connected  to  the  negative  side  of  the  battery.  The 
ammeter  terminal  is  connected  to  the  metal  of  the  motor.  The 
path  of  the  battery  current  is  from  the  positive  side  of  the  battery 
to  and  through  the  primary  of  the  spark-coil  which  is  operating 
at  the  instant,  then  to  the  timer  and  through  it  to  ground,  which 
brings  the  current  to  the  engine  metal,  thence  to  and  through 


250 


ELECTRIC  IGNITION 


the  ammeter  to  the  common  terminal  (— )  of  the  combined  in- 
struments, and  then  through  the  connecting  wire  to  the  negative 
terminal  of  the  battery. 


Storage  Battery 


FlG.   207. 

High-tension  Ignition  System  with  an  Ammeter  and  a  Voltmeter  Permanently 

in  Circuit. 

The  connections  between  the  voltmeter  and  the  battery  must 
not,  include  the  timer,  an  interrupter,  or  the  winding  of  a  coil. 
The  connection  to  the  negative  side  of  the  battery  shows  plainly 
that  it  meets  this  condition.  The  positive  (+)  terminal  of  the 
voltmeter  is  shown  connected  by  a  wire  to  the  contact-block  of 
one  of  the  spark-coils.  In  order  for  this  connection  to  be  correct, 
both  of  the  contact-blocks  of  the  spark-coils  must  be  electrically 
connected  together  by  a  non-inductive  conductor  of  low  resist- 
ance. There  must  also  be  non-inductive,  low-resistance  connec- 
tion between  the  contact-blocks  and  the  terminals  at  the  bottom 
of  the  spark-coil  when  the  switch  is  closed.  The  voltmeter  will 
not  give  the  voltage  of  the  battery  if  this  connection  includes 
the  winding  of  the  spark-coil,  as  is  true  in  many  makes  of  coils. 


JUMP-SPARK  IGNITION   SYSTEMS  251 

If  the  connections  of  the  coil  are  not  known,  a  suitable  place 
for  connecting  the  wire  from  the  (+)  terminal  of  the  voltmeter 
can  generally  be  found  in  the  following  manner: 

Disconnect  one  battery  wire  from  the  spark-coil; 

Connect  the  wire  from  the  (+)  terminal  of  the  voltmeter  to 
the  spark-coil  terminal  to  which  the  battery  wire  is  still  attached ; 

Read  the  voltmeter  while  the  motor  is  running; 

Disconnect  the  voltmeter  wire  from  the  spark-coil  and  connect 
it  to  other  parts  of  the  spark-coil  (except  the  high-tension  ter- 
minal) till  a  place  is  found  which  gives  the  same  voltage  reading 
as  was  obtained  before,  the  motor  still  running; 

Connect  the  other  battery  wire  to  the  spark-coil,  throw  the 
switch  over  to  its  other  position,  and  test  out  for  the  second 
battery  as  before,  omitting  the  battery-wire  terminal  to  which 
the  first  battery  wire  is  connected  at  the  spark-coil. 

If  the  same  point  on  the  spark-coil  answers  for  reading  the 
voltage  of  both  batteries,  then  it  is  a  suitable  place  for  connect- 
ing the  wire  from  the  (+)  terminal  of  the  voltmeter. 

166.  Speed  of  the  Timer.  —  When  a  timer  is  of  the  general 
nature  of  those  described  in  this  chapter,  its  speed  of  rotation  is 
as  follows: 

Half  as  fast  as  the  crank-shaft  of  four-cycle  motors,  which  is 
the  same  speed  as  that  of  the  cam-shaft. 

The  same  as  that  of  the  crank-shaft  of  two-cycle  motors. 


CHAPTER  XVIII. 

HIGH-TENSION  DISTRIBUTER  SYSTEMS  WITH  BATTERY 
CURRENT. 

167.  General.  —  In  systems  of  this  nature  only  one  trans- 
former spark-coil  is  used,  and  the  high-tension  current  from  it 
is  distributed  to  the  spark-plugs,  generally  to  one  plug  at  a  time. 
A  spark-coil  with  a  magnetic  interrupter  of  the  trembler  type  is 
used  in  connection  with  a  slightly  modified  form  of  the  ordinary 
timer  in  some  systems.  In  other  systems  the  spark-coil  is  of  the 
plain  transformer  type  (without  interrupter)  used  in  connection 
with  a  mechanically  operated  contact-maker  which  closes  and 
breaks  the  battery  circuit  at  the  proper  instant  for  ignition. 


High-tension  Distributer  Ignition  System  with  Trembler  Spark-Coil. 

168.   High-tension  Distributer  System  with  Trembler  Spark- 
Coil.  —  In  Fig.   208  one  low-tension  terminal  of  an  ordinary 

252 


HIGH-TENSION   DISTRIBUTER   SYSTEMS  253 

trembler  spark-coil  is  connected  to  all  of  the  four  stationary 
contact-pieces  of  an  ordinary  timer.  This  connection  is  made 
by  a  wire  leading  from  the  transformer  to  one  of  the  stationary 
contacts  of  the  timer,  together  with  a  wire  C,  shown  as  a  circle, 
which  connects  all  of  the  stationary  contacts  of  the  timer  to- 
gether electrically.  By  this  means  the  timer  closes  the  battery 
circuit  four  times  through  the  same  transformer  (the  only  one 
used)  during  one  revolution  of  the  rotor  of  the  timer. 

The  distributer  of  the  high-tension  current  is  represented  as 
a  circular  piece  of  insulating  material  F  inside  of  which  an  in- 
sulated rotor  R  revolves  and  makes  contact  successively  with 
four  insulated  contact-pieces  a,  b,  c,  d.  The  high-tension  ter- 
minal of  the  spark-coil  is  connected  to  the  rotor  of  the  distributer. 
Each  of  the  contact-pieces  a,  b,  c,  d  is  connected  to  a  corre- 
sponding spark-plug.  The  high-tension  current  is  thus  distrib- 
uted to  the  spark-plugs,  one  at  a  time,  in  regular  order. 

The  timer  and  distributer  rotors  revolve  at  the  same  speed 
when  the  timer  has  four  stationary  contact-pieces  as  shown. 
Both  rotors  are  generally  mounted  on  the  same  shaft.  The 
rotor  of  the  distributer  is  brought  into  contact  with  one  of  the 
stationary  contacts  to  which  the  spark-plugs  are  connected, 
each  time  the  circuit  is  closed  by  the  timer.  If  the  timer  had 
only  two  stationary  contacts,  located  diametrically  opposite  each 
other,  then  the  timer  would  have  to  rotate 
twice  as  fast  as  the  distributer.  And  if 
the  timer  had  only  one  stationary  contact- 
piece,  its  rotor  would  have  to  revolve  four 
times  as  fast  as  that  of  the  distributer.  ^ 

rIG.   209. 

^  A  timer  with  only  one  stationary  contact-  Timer  for  High-tension 
piece,  but  with  four  contact-points  on  the  Distributer  System 
rotor,  is  shown  in  Fig.  209.  The  rotative  with  Four  Spark-Plugs, 
speed  of  this  four-pointed  rotor  is  the  same  as  that  of  the  dis- 
tributer rotor  when  there  are  four  spark-plugs. 

The  condenser  A ,  Fig.  208,  is  in  parallel  with  the  magnetically 
operated  interrupter  of  the  spark-coil  in  the  usual  manner.  Con- 
denser B  is  in  parallel  with  the  timer,  so  that  ignition  will  con- 
tinue even  though  the  contact-points  of  the  magnetic  interrupter 


254 


ELECTRIC  IGNITION 


on  the  spark-coil  stick  together  so  as  not  to  break  the  circuit. 
This  feature  has  been  described  in  connection  with  other  systems. 
169.  Mechanically  Operated  Contact-Maker  and  High-tension 
Distributer  System  with  Battery  Current.  —  Fig.  210.  The 
mechanical  contact-maker  which  replaces  the  timer  of  the  pre- 
ceding system  is  represented  by  a  stationary  insulated  piece  H 
which  has  a  contact-point  F,  and  by  a  rocker  which  is  rocked 


Switch 


— I    Contact 
|     Maker    j 

-EE 


L_      _!__      __L_      _J__ 


FIG.  210. 
High-tension  Distributer  System  with  Mechanically  Operated  Contact-Maker. 

on  the  pin  0  by  mechanical  means.  The  movable  contact-point 
E  of  the  rocker  is  thus  brought  into  contact  with  and  separated 
from  the  stationary  contact-point  when  an  ignition  spark  is  to 
be  produced.  This  form  of  contact-maker  is  fully  described  in 
connection  with  the  following  illustrations. 

The  spark-coil  is  of  the  plain  transformer  type  (without  in- 
terrupter). The  condenser  is  part  of  the  spark-coil  and  is  in 
parallel  with  the  contact-maker.  The  distributer  is  of  the  usual 
form  that  has  been  described  in  connection  with  other  systems. 
The  contact-maker  must  close  and  break  the  battery  circuit  four 
times  during  each  revolution  of  the  distributer  for  the  four 
spark-plugs  shown.  If  the  system  were  modified  to  operate  six 
spark-plugs,  then  the  contact-maker  would  have  to  make  and 


HIGH-TENSION   DISTRIBUTER   SYSTEMS  255 

break  the  battery  circuit  six  times  during  one  revolution  of  the 
distributer,  and  similarly  for  whatever  number  of  spark-plugs 
are  used.  The  distributer  must  have  as  many  stationary  con- 
tacts as  there  are  spark-plugs  to  be  operated  by  it.  The  rotor 
of  the  distributer  may  be  mounted  on  the  shaft  that  operates 
the  contact-maker,  in  order  to  obtain  a  compact  form.  This  is 
the  more  usual  construction. 

170.  Unisparker.  —  The  constructive  form  of  the  contact- 
maker,  some  of  whose  parts  are  shown  in  connection  with  the 
preceding  ignition  system,  is  illustrated  in  Fig.  211.  The  driving 


FIG.  211. 
Contact-Maker  of  Unisparker. 

shaft  A- A  rotates  counter-clockwise,  as  indicated  by  the  arrow. 
It  has  four  notches  to  correspond  to  the  same  number  of  spark- 
plugs to  be  operated.  As  the  shaft  A- A  rotates,  each  of  its  notches 
in  turn  catches  the  hook  at  the  end  of  the  snapper  A-D  and  draws 
the  snapper  forward  against  the  resistance  of  the  coiled  tension 
spring  A  -E,  until  the  pressure  of  the  cylindrical  surface  of  the  shaft 
against  the  snapper  disengages  the  hook  from  the  notch.  The 
position  of  these  parts  at  the  instant  of  disengagement  is  shown 
in  Fig.  212.  The  snapper  then  snaps  back,  and  while  doing  so 
the  point  of  its  hook  rides  on  the  cylindrical  surface  of  the  shaft. 
This  action  presses  the  snapper  against  the  lip  L  on  the  contact 
arm  A-F  and  causes  the  latter,  together  with  the  contact-point 
Vj  to  rock  on  the  pin  0  so  as  to  press  the  contact-point  V 


256  ELECTRIC  IGNITION 

against  the  point  of  the  stationary  contact  screw  A-H.  Con- 
tact-point V  is  mounted  on  a  flat  spring.  When  the  snapper 
has  moved  to  the  position  shown  in  Fig.  213,  it  passes  out  of 
contact  with  the  lip  L,  and  the  contact-points  are  then  rapidly 
separated  by  the  action  of  the  coiled  spring  A-G,  which  acts 
on  the  rocker  arm  A-F  in  such  a  manner  as  to  rock  it  in  the 
direction  to  separate  the  contact-points.  Pressing  the  contact- 


FlG.    212.  FlG.    213. 

Unisparker  Contact-Maker  in  Position         Contact-Maker  with  Contact-Points 
just  before  making  Contact.  Pressed  Together. 

points  V  and  A-H  together  closes  the  battery  circuit.  The  dura- 
tion of  the  time  of  contact  is  regulated  by  adjusting  the  insulated 
contact-screw  A-H  in  the  stationary  part  which  holds  it. 

The  snapper  A-D  is  of  very  light  weight,  and  the  spring  A-E  is 
of  sufficient  strength  to  draw  the  snapper  back  with  great  rapidity. 
This  movement  is  sufficiently  rapid  to  give  the  same  duration  of 
contact  between  the  points  V  and  A  -H  whatever  the  speed  of  ro- 
tation of  the  shaft  A- A  up  to  speeds  as  high  as  are  necessary  for 
ignition.  The  primary  circuit  must  of  course  be  kept  closed 
long  enough  to  allow  the  battery  current  to  reach  a  strength  that 
will  produce  a  spark  at  the  spark-plug  when  the  circuit  is  broken 
by  the  action  of  the  contact-maker.  If  the  adjustment  is  such 
as  to  make  the  period  of  contact  longer  than  this,  a  stronger, 
or  hotter,  spark  is  produced  at  the  igniter.  The  strength  of  the 
ignition  spark  can  therefore  be  regulated  by  adjusting  the  con- 


HIGH-TENSION   DISTRIBUTER  SYSTEMS 


257 


tact  screw  A-H.    Only  one  ignition 
spark  is  produced  for  each  ignition. 

An  external  view  of  the  unisparker  is 
shown  in  Fig.  214.  The  contact-maker 
is  in  the  lower  part  of  the  casing,  and 
the  upper  part  contains  the  high-ten- 
sion distributer.  Five  wires  connect 
to  the  latter  at  the  top  of  the  casing. 
One  of  these  is  at  the  center  of  the  top 
for  bringing  high-tension  current  from 
the  transformer.  The  other  four  are 
for  carrying  current  to  the  spark-plugs. 
The  terminals  for  the  latter  four  wires 
are  in  a  circle  at  equal  distances  from 
each  other.  The  arm  projecting  to- 
ward the  left  just  beneath  the  casing 
is  the  timing  lever  for  advancing  and 
retarding  the  spark.  The  rotating 


FIG.  214.     (See  also  Figs.  211. 
212,  213  and  215.) 

Unisparker.  Atwater  Kent 
Manufacturing  Works, 
Philadelphia,  Pa. 


\ 


FIG.  215. 
Parts  of  Fig.  214. 

parts  are  driven  by  the  shaft  that  projects  from  the  bottom  of 
the  casing. 

The  interior  construction  is  shown  in  Fig.  215.     The  com- 


258  ELECTRIC  IGNITION 

bined  cover  and  distributer  plate  is  at  the  right-hand  side  of 
the  illustration,  and  the  distributer  rotor  in  the  center.  The 
contact-maker,  at  the  left-hand  side  of  the  illustration,  has  a 
condenser  enclosed  in  the  cylinder  which  can  be  seen  to  the  right 
of  the  driving  shaft. 

The  coil  box  and  switch  to  be  used  in  connection  with  the 
combined  contact-maker  and  distributer  shown  in  the  last  two 


FIG.  216. 
Non-trembler  Transformer  Spark- Coil  and  Switch  for  use  with  Unisparker. 

illustrations  is  seen  in  Fig.  216.  No  condenser  is  required  in  the 
coil  box  when  there  is  one  in  the  unisparker,  as  shown  in  the 
preceding  illustration. 

171.  Combined  Contact-Maker,  Spark-Coil,  and  Distributer. — 
Fig.  217.  A  contact-maker  of  the  kind  just  described,  a  trans- 
former spark-coil  (without  a  trembler),  a  condenser,  a  high- 
tension  distributer,  and  a  switch  are  all  grouped  together  in  this 
device.  The  contact-maker  is  inside  of  the  small  cover  A  at 
the  top  of  the  box.  B  is  a  starting  button  for  starting  the  motor 
on  spark,  provided  the  cylinder  of  the  motor  contain  combustible 
mixture.  C  is  a  wing-nut  for  holding  the  cover  on  the  contact- 
maker. 

The  distributer  D  is  in  the  form  of  a  shaft  with  four  winglike 
blades,  of  which  one  is  lettered  E.  The  high-tension  current 
is  brought  to  the  distributer  through  the  brush-holder  F,  which 
holds  a  brush  (carbon  pencil)  that  is  forced  outward  by  a  spring 


HIGH-TENSION   DISTRIBUTER  SYSTEMS 


259 


so  as  to  make  contact  with  the  shaft  of  the  distributer.  G  is 
the  distributer  board  which  carries  four  high-tension  binding 
posts  (terminals),  each  lettered  H,  for  making  connection  to  the 
wires  leading  to  the  spark-plugs.  Each  of  the  distributer  blades 
E  passes  near  to,  or  makes  light  contact  with,  the  inner  end  of 
the  corresponding  terminal  H.  Four  push-buttons,  each  lettered 
/,  are  provided  for  cutting  off  the  ignition  from  the  correspond- 


FIG.  217. 

Atwater  Kent  Combined  Contact-Maker,  Spark-Coil  and  High-tension  Distributer 
for  Four  Spark-Plugs. 

ing  cylinders  of  the  motor.  The  housing  /  contains  a  spiral 
sleeve  which  drives  the  rotors  of  the  contact-maker  and  dis- 
tributer. This  sleeve  is  moved  by  the  operator  by  means  of  the 
spark-control  lever  at  his  hand,  so  as  to  advance  or  retard  the 
spark.  M  is  the  switch,  N  the  switch  plug,  and  O  the  switch 
handle.  The  binding  post  for  connecting  to  the  positive  (car- 
bon) side  of  the  battery  is  shown  at  P.  The  holes  Q  are  for 


260  ELECTRIC  IGNITION 

screws  or  bolts  to  fasten  the  device  in  place.  R  is  an  oil  tube. 
S  is  a  clamping  collar  for  setting  the  shaft  D  so  as  to  have  the 
spark  occur  at  the  correct  instant. 

172.  Comparison  of  Unisparker  and  Ordinary  Timer.  —  The 
contact-maker  described  in  this  chapter  is  decidedly  more  eco- 
nomical of  electricity,  and  therefore  of  batteries,  than  a  timer  of 
the  ordinary  type.  The  ordinary  timer  must  keep  the  battery 
circuit  closed  long  enough,  at  the  highest  speed  of  the  motor, 
to  allow  the  primary  current  to  become  strong  enough  to  produce 
a  sufficiently  large  ignition  spark  when  the  current  is  interrupted ; 
or,  the  timer  must  keep  the  circuit  closed  long  enough  for  the 
magnetic  trembler  of  the  spark-coil  to  interrupt  the  current.  If 
the  motor  is  slowed  down  to  half  speed,  then  two  or  more  igni- 
tion sparks  will  be  produced  by  a  trembler  interrupter  for  each 
ignition,  or  if  there  is  no  trembler  interrupter  the  current  will 
flow  twice  as  long,  and  at  least  twice  as  much  electricity  will  be 
used  for  the  corresponding  one  ignition  as  is  necessary.  A  similar 
statement  is  true  relative  to  still  slower  speeds  of  the  motor. 
The  electricity  used  for  producing  ignition  sparks  after  the  first 
one  for  one  ignition  is  wasted.  The  same  is  true  of  current  that 
flows  after  the  current  has  become  strong  enough,  when  there 
is  no  magnetic  interrupter  of  the  trembler  type.  This  waste 
represents  the  difference  between  the  amount  of  electricity  that 
is  used  by  the  contact-maker  that  has  been  described,  and  the 
ordinary  form  of  timer. 


CHAPTER  XIX. 
SPARK-PLUGS  IN  SERIES,  AND  IN  SERIES-SHUNT. 

173.  Two  jump-spark  igniters  can  be  operated  in  series  with 
each  other  on  current  from  the  same  spark-coil.  An  ignition 
system  of  this  nature  is  shown  in  Fig.  218  with  a  trembler 
spark-coil.  The  spark-coil  of  necessity  has  four  terminals,  —  two 
high-tension  and  two  low-tension.  The  primary  and  secondary 
terminals  of  the  coil  are  not  connected  together.  The  timer 


FIG.  218. 

Two  Spark-Plugs  in  Series  with  Each  Other  in  a  High-tension  Ignition  System. 

has  two  stationary  contact-pieces,  diametrically  opposite  each 
other.  These  contact-points  are  connected  together  by  a  wire 
so  that  the  timer  closes  the  battery  circuit  twice  each  revolution 
at  equal  intervals.  The  spark-plugs  are  represented  as  in  place 
in  a  motor  of  the  four-cycle  two-cylinder  opposed  type.  The 
outer  bushing  of  the  spark-plug  is  grounded  by  its  contact  with 
the  metal  of  the  motor  in  the  ordinary  manner,  so  that  these 
bushings  are  electrically  connected  together.  The  plugs  are  of 
the  ordinary  jump-spark  type. 

261 


262  ELECTRIC  IGNITION 

When  the  battery  circuit  is  closed  by  the  timer,  the  high- 
tension  current  flows  from  one  of  the  terminals  of  the  spark-coil 
to  the  insulated  spindle  of  one  of  the  spark-plugs,  jumps  the 
spark-gap  of  the  plug  to  the  outer  bushing  of  the  plug  and  the 
metal  of  the  motor,  then  flows  through  the  metal  of  the  motor  to 
the  outer  bushing  of  the  other  spark-plug,  jumps  the  spark-gap  to 
the  insulated  spindle  of  that  plug,  and  then  flows  back  to  the 
spark-coil.  A  spark  jumps  at  the  same  instant  at  both  plugs. 
The  sparks  pass  twice  as  often  as  necessary  at  each  plug,  since 
the  ignitions  occur  alternately  in  the  two  cylinders. 

The  timer  with  the  two  stationary  contacts  rotates  at  half 
the  speed  of  the  crank-shaft  (at  the  same  speed  as  the  cam-shaft) 
for  a  four-cycle  motor.  A  timer  with  only  one  stationary  con- 
tact-piece and  one  arm  on  the  rotor  can  be  used  if  it  is  rotated  at 
the  same  speed  as  the  crank-shaft. 

This  system  has  a  feature  relative  to  backfiring  into  the  intake 
that  does  not  appear  in  other  systems.  If  the  motor  is  rotated 
at  very  slow  speed,  as  when  starting  it,  and  the  ignition  is  very 
much  retarded  (set  very  late),  then  the  mixture  in  both  cylinders 
may  be  ignited  at  the  same  instant.  Thus,  suppose  the  crank- 
shaft and  pistons  are  in  the  positions  shown  in  the  figure  when 
the  sparks  jump,  and  the  speed  of  rotation  is  slow.  One  piston 
is  on  its  impulse  stroke,  and  the  other  on  its  suction  stroke.  The 
one  on  the  suction  stroke  may  have  drawn  in  combustible  mix- 
ture enough  to  be  ignited,  and,  since  the  inlet  valve  of  that 
cylinder  is  open  to  admit  the  mixture,  the  flame  will  run  back 
into  the  inlet  passage,  thus  backfiring  the  incoming  charge. 
This  action  occurs  frequently  in  small  motors  that  are  cranked 
by  hand  when  this  system  of  ignition  is  used.  Backfiring  of 
course  occurs  in  motors  that  do  not  have  this  kind  of  an  ignition 
system,  on  account  of  entirely  other  causes.  These  other  causes 
will  cause  backfiring  in  the  series-plug  ignition  system,  as  well  as 
in  the  other  systems  of  ignition. 

174.  Series-shunt  Connection  of  Spark-Plugs.  —  A  diagram- 
matic representation  of  a  high-tension  ignition  system  in  which 
current  is  supplied  by  one  transformer  to  the  two  spark-plugs 
for  two  combustion  chambers,  one  plug  for  each  combustion 


SPARK-PLUGS   IN   SERIES,  AND   IN   SERIES-SHUNT 


263 


chamber,  and  which  is  provided  with  a  short-circuiter  for  shunt- 
ing the  current  from  the  spark-plug  at  which  no  spark  is  desired 
at  the  moment  of  ignition  in  the  combustion  chamber  that  con- 
tains a  compressed  charge,  is  shown  in  Fig.  219. 

The  transformer  is  of  the  non-trembler  type  with  the  primary 
and  secondary  windings  not  connected  to  each  other.     Low- 


FIG.  219.     (See  also  Figs.  220  and  221.) 
Series-shunt  Connection  of  Two  Spark-Plugs  in  a  High-tension  Ignition  System. 

tension  current  is  supplied  either  by  a  battery  or  by  a  dynamo, 
either  of  which  can  be  thrown  into  the  circuit  by  means  of  the 
two-point  switch  whose  blade  is  connected  to  the  terminal  A  of 
the  primary  winding  of  the  transformer.  The  other  low-tension 
terminal  B  of  the  transformer  is  connected  to  one  side  of  the 
condenser  C.  The  opposite  side  of  the  condenser  is  connected 
to  the  battery  and  dynamo,  and  is  also  grounded  by  the  wire 


264  ELECTRIC  IGNITION 

DE  which  is  connected  to  the  metal  of  the  engine  at  E.  The 
primary  terminal  B  is  also  connected  to  the  insulated  stationary 
contact  F  of  the  mechanically  operated  interrupter.  The  mov- 
able contact  G  of  the  interrupter  is  attached  to  a  spring-blade  H 
which  is  held  in  place  by  the  grounded  piece  /.  A  piece  of  insu- 
lating material  J  is  fastened  to  the  spring-blade  so  that  the 
lobes,  or  projections,  of  the  rotor  Rf  will  strike  it  as  the  rotor 
revolves.  The  spring  is  pressed  down  by  the  lobe  of  the  rotor 
so  as  to  bring  the  contact-points  together  and  close  the  primary 
circuit.  The  circuit  is  immediately  broken  as  the  lobe  passes 
out  of  contact  with  the  insulation  /.  It  can  be  seen  that  the 
connections  are  such  that  the  primary  circuit  cannot  be  closed 
by  the  interrupter  unless  the  ground  wire  DE  from  the  con- 
denser is  in  place.  It  is  therefore  impossible  to  operate  the 
system  while  the  condenser  is  not  connected  into  it  so  as  to  pro- 
tect the  contact-points  of  the  interrupter,  as  well  as  to  add  to 
the  effectiveness  of  the  operation. 

The  novel  feature  of  this  system  lies  in  the  short-circuiting, 
or  shunting,  device  connected  into  the  high-tension  circuit.  This 
device  resembles,  in  a  general  way,  a  high-tension  distributer, 
but  acts  in  the  reverse  manner.  The  short-circuiter  cuts  off  the 
current  from  the  spark-plug  at  which  no  spark  is  desired  at  the 
instant  of  ignition  at  the  other  plug,  instead  of  directing  current 
to  the  plug  at  which  ignition  is  to  occur,  the  latter  being  the 
method  of  the  ordinary  high-tension  distributer. 

The  spark-plugs  M  and  N  are  connected  in  series  with  each 
other  to  the  secondary  terminals  S  and  T  of  the  transformer. 
The  insulated  contact-piece  K  of  the  short-circuiter  is  also  con- 
nected to  the  high-tension  terminal  5  of  the  transformer.  Like- 
wise the  other  insulated  contact-piece  L  of  the  short-circuiter  is 
connected  to  the  high-tension  terminal  T  of  the  transformer. 
The  grounded  rotor  R"  of  the  short-circuiter  makes  contact 
alternately  with  L  and  K  during  its  rotation.  The  two  rotors, 
R'  and  R",  of  the  interrupter  and  short-circuiter  respectively, 
rotate  at  the  same  speed.  They  are  ordinarily  mounted  on  the 
same  shaft  as  one  piece  of  apparatus,  although  shown  separately 
for  clearness  in  the  diagram. 


SPARK-PLUGS  IN   SERIES,   AND  IN  SERIES-SHUNT        265 

When  the  rotors  have  revolved  somewhat  less  than  a  quarter- 
revolution  from  the  positions  shown,  the  short-circuiter  rotor 
makes  contact  with  the  grounded  contact-piece  L.  These  two 
parts  remain  in  contact  while,  during  further  rotation  of  the 
rotors,  the  primary  circuit  is  made  and  broken  at  the  interrupter. 
The  induced  high-tension  current  passes,  assuming  a  direction 
of  flow,  from  the  terminal  S  to  the  insulated  spindle  of  the  spark- 
plug M,  jumps  the  spark-gap  in  M,  thus  reaching  the  metal  of 
the  engine,  through  which  it  flows  to  the  grounded  rotor  R"  of 
the  short-circuiter,  thence  to  the  contact-piece  L,  since  R"  and 
L  are  in  contact  with  each  other,  and  on  to  the  other  high-tension 
terminal  T  of  the  transformer.  No  current  flows  through  the 
spark-plug  N  during  this  operation,  since  the  resistance  of  its 
spark-gap  is  enormous  in  comparison  with  that  of  the  parallel 
circuit  through  the  short-circuiter.  The  action  is  similar  for 
producing  a  spark  at  the  spark-plug  N  when  the  rotors  have 
revolved  a  half-revolution  farther.  An  ignition  spark  is  thus 
produced  first  at  one  spark-plug  and  then  the  other,  as  required. 

175.  Constructive  Form  of  Series-shunt  Spark-plug  Ignition 
System.  —  Fig.  220.  This  shows  more  clearly  the  nature  of  the 
apparatus  used  in  the  system  illustrated  diagrammatically  in 
the  preceding  figure.  Corresponding  parts  are  designated  by  the 
same  letters  in  the  two  figures,  as  far  as  possible.  In  Fig.  220 
the  rotor  R  is  a  combination  of  the  two  rotors  R'  and  R"  of  the 
preceding  figure.  P  and  Q  are  merely  suitable  terminals  by 
means  of  which  the  high-tension  wires  are  connected  to  the 
insulated  terminals  K  and  L  of  the  short-circuiter.  The  short- 
circuiting  pin  which  is  a  part  of  R  corresponds  to  the  rotor  arm 
R"  of  the  diagram.  The  switch  used  is  of  the  snap  type,  which 
eliminates  the  possibility  of  drawing  an  injurious  arc  in  the  switch 
when  changing  connections,  as  when  switching  from  the  dynamo 
to  the  battery,  and  vice  versa. 

The  stationary  contact-piece  F  of  the  interrupter  is  cup-shaped, 
and  threaded  on  the  inside  so  as  to  be  adjustable.  This  piece, 
together  with  the  part  into  which  it  screws,  is  insulated.  The 
cup  in  the  stationary  contact-piece  can  be  filled  with  oil,  in  which 
the  breaking  of  the  circuit  will  occur  for  each  ignition.  The  oil 


266 


ELECTRIC  IGNITION 


protects  the  contact-points  against  burning  and  fusing.  The 
short-circuiter  contacts  K  and  L  are  mounted  on  insulating 
fiber  pieces  which  are  clamped  into  the  stationary  frame  of  the 


FIG.  220.     (See  also  Figs.  219  and  221.) 

Constructive  Form  of   Series-shunt   Spark-plug  Ignition   System.    The  Bruce- 
Macbeth  Engine  Company,  Cleveland,  Ohio. 


combined  interrupter  and  circuit-breaker.  This  frame  is  adjust- 
able rotatively,  and  is  clamped  in  position  by  means  of  the 
thumbscrew  shown  at  the  top. 

The  combined  interrupter  and  short-circuiter  is  shown  more 
in  detail  in  Fig.  221. 

The  above  apparatus  is  intended  for  use  on  a  stationary  engine. 
The  spark-coil  used  is  much  larger  than  those  customarily  used 
for  small  motors,  such  as  those  of  motor  boats  and  automobiles. 


SPARK-PLUGS  IN   SERIES,  AND   IN   SERIES-SHUNT        267 


CHAPTER  XX. 

INTERRUPTER  MAGNETOS  AND    JUMP-SPARK  IGNITION 
SYSTEMS  WITH  MAGNETO   CURRENT   ONLY. 

176.  Introductory.  —  This  chapter  is  intended  to  describe  the 
more   distinctive   types  of  magnetos  that  are  equipped  with 
interrupters  for  making  and  breaking  the  primary  circuit,  or 
some  part  of  it,  at  the  instant  a  jump-spark  is  desired  for  ignition, 
and  with  a  high-tension  distributer  for  directing  the  secondary 
current  to  the  spark-plugs  in  consecutive  order.     Some  simple 
jump-spark   ignition   systems  using  magneto  current  only  are 
presented  in  order  to  make  clear  the  operation  of  the  magneto. 
A  rotative  armature  of  the  shuttle-wound  type  is  used  most 
frequently  in  the  ignition-system  diagrams,  but  this  is  merely 
a  matter  of  convenience.     Alternating-current  magnetos  with 
other  types  of  armatures  could  be  used  equally  well. 

Magnetos  which  are  especially  designed  to  operate  in  connec- 
tion with  batteries  in  combination,  or  dual  ignition  systems,  are 
not  described  in  this  chapter,  but  are  described  later  in  connec- 
tion with  their  ignition  systems. 

177.  Interrupted  Primary  Current  Magneto  Ignition  System. 
—  Fig.  222.     The  magneto  has  a  single-wound  armature  of  the 

shuttle  type,  which  rotates  between  the  pole-pieces  of  the  mag- 
nets in  the  usual  manner.  One  end  of  the  armature  winding  is 
"  grounded  "  by  connection  to  the  core  of  the  armature.  The 
other  end  of  this  winding  is  connected  to  a  transformer  spark- 
coil  at  the  junction  of  the  primary  and  secondary  windings. 
This  connection  is  made  through  a  suitable  brush  (not  shown) 
which  has  rubbing  contact  with  the  insulated  part  that  rotates 
with  the  armature  and  to  which  the  insulated  end  of  the  arma- 
ture winding  is  electrically  connected.  The  low-tension  ter- 
minal of  the  primary  winding  P  of  the  transformer  spark-coil 
is  connected  to  an  insulated  contact  block  B  of  a  mechanically 

268 


INTERRUPTER   MAGNETOS   AND  JUMP-SPARK  IGNITION     269 

operated  interrupter.  The  interrupter  is  part  of  the  magneto, 
although  shown  separate  from  it  for  convenience.  The  movable 
contact-point  of  the  interrupter  is  fastened  to  the  interrupter 
arm,  or  lever  M ,  which  keeps  the  contact-points  pressed  together 
except  when  the  arm  is  lifted  by  the  two-lobed  cam  C  as  the  cam 
rotates.  This  cam  is  mounted  on  the  armature  shaft  and 
rotates  with  the  armature.  The  left-hand  end  of  the  interrupter 


FIG.  222. 

Jump-spark  Ignition  System  with  a  Low-tension  Magneto,  a  High-tension 
Distributer,  a  Separate  Transformer  and  a  Mechanical  Interrupter  for  Breaking 
the  Magneto-Transformer  Circuit. 

arm  is  fastened  to  a  block  which  has  ground  connection  with 
the  body  of  the  magneto.  A  condenser  is  in  parallel  with  the 
interrupter. 

The  cam  C  is  set  in  such  a  position  relative  to  the  armature 
of  the  magneto  that  the  interrupter  breaks  the  primary  circuit 
while  the  armature  is  passing  through  the  position  which  corre- 
sponds more  or  less  nearly  to  the  maximum  flow  of  current 
through  the  armature  winding  and  the  primary  winding  of  the 
spark-coil.  The  primary  circuit  is  kept  closed  at  the  interrupter 
during  a  quarter-revolution  or  so  of  the  armature  preceding  the 


270  ELECTRIC  IGNITION 

interruption  of  the  current,  during  which  quarter-revolution  the 
current  gradually  increases  from  nothing  to  its  maximum  value. 
The  maximum  value  of  the  current  occurs  when  the  armature 
has  rotated  slightly  past  the  position  shown;  also  when  it  has 
rotated  slightly  more  than  half  a  revolution  past  the  position 
shown. 

The  interruption  of  the  current  that  flows  through  the  armature 
and  the  primary  of  the  transformer  spark-coil  induces  a  high- 
tension  current  momentarily  in  the  secondary  winding  S  of  the 
transformer.  The  high-tension  terminal  of  the  transformer  is 
connected  to  the  insulated  rotor  R  of  a  distributer  which  directs 
the  current  to  the  spark-plugs  in  regular  order  as  required.  The 
high-tension  current,  after  jumping  the  spark-gap  at  the  plug, 
passes  through  ground  to  the  metal  of  the  magneto,  thence  to 
and  through  the  magneto  winding  to  the  junction  end  of  the 
secondary  of  the  transformer.  It  is  possible  that  at  least  some 
of  the  high-tension  current  passes  through  the  interrupter  by 
jumping  across  the  opening  between  the  contact-points  while 
they  are  separated  to  break  the  primary  circuit.  The  distributer 
is  part  of  the  magneto.  The  rotor  of  the  distributer  is  generally 
driven  by  gears,  one  on  the  armature  shaft  and  the  other  on  the 
shaft  that  carries  the  rotor  of  the  distributer.  For  four  spark- 
plugs, each  in  its  own  combustion  chamber,  the  distributer  rotor 
revolves  at  half  the  speed  of  the  magneto  armature.  The  gear 
on  the  distributer  shaft  therefore  has  twice  as  many  teeth  as  its 
mate  on  the  armature  shaft.  The  rotative  speed  of  the  armature 
shaft  must  be  the  same  as  that  of  the  crank-shaft  of  a  four-cycle 
motor  that  has  four  combustion  chambers.  For  a  four-cycle 
motor  that  has  six  combustion  chambers,  the  rotative  speed  of 
the  magneto  armature  must  be  one  and  a  half  times  that  of  the 
motor  crank-shaft. 

The  ignition  can  be  cut  out  by  closing  the  switch,  which  is 
shown  open.  Closing  this  switch  short-circuits  the  armature  of 
the  magneto  and  thus  practically  leaves  the  spark-coil  out  of 
the  circuit.  Very  little  of  the  armature  current  then  passes 
through  the  spark-coil,  since  the  resistance  of  its  primary  wind- 
ing is  much  greater  than  that  of  the  short  circuit  through  the 


INTERRUPTER  MAGNETOS  AND  JUMP-SPARK  IGNITION     271 

closed  switch.     The  resistance  of  the  primary  of  the  spark-coil 
is  both  ohmic  and  inductive. 

A  safety  spark-gap  is  generally  provided  in  the  secondary 
circuit  to  prevent  overstraining  of  the  insulation  of  the  high- 
tension  circuits  in  case  one  of  the  wires  becomes  disconnected 
from  its  spark-plug.  No  safety  spark-gap  is  shown  in  the  dia- 
gram, it  being  omitted  in  order  to  keep  the  diagram  as  simple  as 
possible.  Safety  spark-gaps  will  be  shown  in  connection  with 
the  constructive  forms  of  magnetos. 


FIG.  223. 

Jump-spark  Ignition  System  with  a  Low-tension  Magneto,  a  High-tension  Dis- 
tributer, a  Separate  Transformer  and  a  Mechanical  Interrupter  in  a  Shunt  Circuit. 

178.   Interrupted  Shunt-current  Magneto  Ignition  System.  — 

Fig.  223.  The  primary  circuit  is  never  broken  in  this  system. 
The  interrupter  is  located  in  a  shunt  circuit  which  shunts  the 
major  part  of  the  primary  current  away  from  the  spark-coil 
during  the  time  the  interrupter  contacts  are  closed. 

During  the  rotation  of  the  magneto  armature  from  its  zero- 
current  position  to  its  position  of  maximum  current  the  in- 
terrupter is  closed  and  most  of  the  armature  current  is  in 
consequence  shunted  from  the  spark-coil  and  passes  through  the 


272  ELECTRIC  IGNITION 

interrupter.  When  the  magneto  current  is  at  or  near  its  maxi- 
mum value,  the  interrupter  breaks  the  shunt  circuit.  This 
interruption  of  the  shunt  current,  together  with  the  action  of 
the  condenser,  causes  a  sudden  impulse  of  current  through  the 
primary  winding  of  the  spark-coil.  The  inductive  action  of  this 
impulse  current  produces  a  momentary  high-tension  current  in 
the  secondary  of  the  transformer.  The  high-tension  current  is 
distributed  to  the  spark-plugs  in  the  manner  that  has  already 
been  described. 

Closing  the  switch  keeps  the  shunt  circuit  permanently  closed, 
thus  cutting  the  spark-coil  out  of  operation  and  stopping  ignition. 

179.  Shunted-current  Magneto  Ignition  System.  —  If  the  cam 
C  in  Fig.  223  is  set  forward  on  its  shaft  to  the  extent  of  about 
a  quarter-revolution  relative  to  the  armature  of  the  magneto, 
then  one  of  the  lobes  on  the  cam  would  keep  the  interrupter 
contacts  separated  during  the  time  the  armature  is  rotating  from 
its  position  of  zero  current  to  the  position  at  or  near  maximum 
current.     The  position  of  the  armature  at  maximum  current  is  a 
little  later  than  shown  in  the  figure.     The  interrupter,  or  more 
properly  contact-maker  in  this  application,  would  then  close  the 
shunt  circuit.     The  closing  of  the  shunt  circuit  would  divert  the 
armature  current  from  the  spark-coil,  through  whose  winding 
it  flows  while  the  contact-points  of  the  interrupter  are  separated. 
The  shunting  of  the  armature  current  through  the  interrupter 
causes  a  sudden  drop  of  current  in  the  primary  winding  of  the 
transformer  spark-coil,  and  a  high-tension  current  is  consequently 
induced  in  the  secondary  of  the  spark-coil. 

This  system  has  the  distinctive  feature  that  the  interrupter 
contacts  can  be  separated  at  the  instant  when  little  or  no  current 
is  flowing  through  the  armature  and  interrupter.  Burning  and 
fusing  of  the  contact-points,  therefore,  do  not  occur.  Other 
features  of  the  system  seem  to  have  prevented  its  coming  into 
extensive  use,  however. 

180.  High-tension  Magneto  with  Single- wound  Armature.  - 
If  all  of  the  apparatus  except  the  spark-plugs  and  switch  of  the 
preceding  figures  of  this  chapter  are  assembled  in  one  piece  of 
apparatus,  the  combination  is  a  high-tension  magneto,  since  it 


INTERRUPTER  MAGNETOS   AND  JUMP-SPARK  IGNITION     273 

will  deliver  high-tension  current  suitable  for  jump-spark  ignition 
without  the  aid  of  any  exterior  apparatus  for  generating  the 
high-tension  current.  High-tension  magnetos  of  this  type  (with 
the  transformer  a  part  separate  from  the  armature)  are  used  to 
a  considerable  extent.  The  transformer  in  such  cases  is  gen- 
erally located  in  the  space  between  the  armature  and  the  crown 
of  the  magnets. 

181.   Double-wound  High-tension  Magneto  Ignition  System. — 
Fig.   224.     The  magneto  illustrated  diagrammatically  has  an 


Switch 

"Ground1 
FlG.   224. 
High-tension  Magneto  Connected  to  Spark-Plugs.     A  Complete  Ignition  System. 


armature  of  the  shuttle  type  with  two  windings,  primary  and 
secondary.  The  beginning  of  the  primary  winding  is  grounded 
by  fastening  the  end  of  the  wire  to  the  core  A  of  the  armature, 
and  the  wire  is  wound  over  the  entire  core-neck  next  to  the  core. 
The  end  of  the  primary  winding  is  connected  to  the  beginning 
of  the  secondary  winding,  and  the  latter  is  wound  over  the 
primary.  The  high-tension  terminal  of  the  secondary  winding 
is  connected  to  the  high-tension  distributer.  The  junction  of 
the  two  windings  of  the  armature  is  connected  to  the  stationary 


274  ELECTRIC  IGNITION 

insulated  contact-piece  B  of  the  mechanically  operated  inter- 
rupter. The  movable  contact  arm  M  of  the  interrupter  is 
grounded  to  the  metal  of  the  magneto.  The  interrupter  arm  is 
actuated  by  the  two-lobed  cam  C,  which  is  mounted  on  the 
armature  shaft  and  rotates  at  the  same  speed  as  the  armature. 

The  primary  circuit  is  kept  closed  at  the  interrupter  while 
the  armature  of  the  magneto  is  rotating  from  a  position  about  a 
quarter-revolution  earlier  than  that  in  which  it  is  shown,  to  a 
position  slightly  later  than  that  shown.  During  this  approxi- 
mate quarter-revolution  of  the  armature,  the  current  in  the 
primary  winding  increases  from  zero  to  its  maximum  value,  or 
approximately  so.  During  the  same  part  revolution,  electro- 
motive force  is  also  generated  in  the  secondary  winding  of  the 
armature,  but  not  sufficient  to  produce  a  pressure  that  will  cause 
a  spark  to  jump  across  the  spark-gap  of  the  spark-plug.  The 
interrupter  breaks  the  primary  circuit  while  the  primary  current 
is  at  or  near  its  maximum  value,  and  the  consequent  sudden 
stoppage  of  current  in  the  primary  of  the  armature  induces  a 
pressure  in  the  secondary  high  enough  to  cause  a  spark  at 
the  spark-plug. 

The  two-lobed  cam  of  the  interrupter  causes  the  circuit  to 
be  broken  twice  during  each  revolution  of  the  armature,  and 
two  ignition  sparks  are  thus  produced  during  one  revolution  of 
the  magneto  armature. 

The  condenser  is  in  parallel  with  the  interrupter  in  the  usual 
manner. 

Ignition  can  be  cut  out  by  closing  the  switch  shown.  This 
short-circuits  the  primary  winding  of  the  armature  and  pre- 
vents the  sudden  cessation  of  the  primary  current  which  occurs 
when  the  switch  is  open  as  shown  and  the  interrupter  breaks 
the  circuit.  The  pulsating  current  which  occurs  in  the  primary 
while  the  switch  is  closed  will  not  produce  a  spark  at  the  spark- 
plug. 

The  distributer  is  of  the  usual  type,  driven  at  half  the  speed 
of  the  armature  for  four  ignition  plugs.  For  six  ignition  plugs 
the  rotor  of  the  distributer  must  be  driven  at  one-third  of  the 
speed  of  the  armature.  The  distributer  for  six  spark-plugs  has 
six  contact-points  equally  spaced  relative  to  each  other.  The 


INTERRUPTER  MAGNETOS  AND   JUMP-SPARK  IGNITION     275 


interrupter,  distributer,  and  condenser  are  all  component  parts  of 
the  magneto. 

182.  A  Bosch  High-tension  Magneto  with  Double-wound 
Rotary  Armature  is  shown  in  Figs.  225,  226,  and  227.  Of  the 
latter  two  figures,  one  is  a  longitudinal  section  and  the  other  a 
view  on  the  interrupter  end.  The 
corresponding  wiring  diagram  is 
given  in  Fig.  228,  and  the  parts  are 
shown  separated  in  Plates  I,  II,  and 
III.  Modified  forms  of  some  of  these 
parts  are  shown  in  Plate  IV.  The 
system  is  the  same  as  that  shown  in 
Fig.  224.  It  may  be  noticed  that 
the  interrupter  (contact-breaker)  le- 
ver and  the  "stationary"  contact- 
piece  of  the  interrupter  rotate  with 
the  armature. 

Referring  to  Figs.  226,  227,  and  FIG 
228,  the  beginning  of  the  primary 
winding  is  metallically  connected 
(grounded)  to  the  metal  of  armature  High-tension  Magneto  for  Four 
core.  The  end  of  the  primary  wind-  Spark-Plugs.  Bosch  Magneto 
ing  is  connected  to  the  insulated  brass  Company,  New  York  City, 
plate  i,  which  is  also  connected  to  one  side  of  the  condenser. 
The  other  side  of  the  condenser  is  grounded  on  the  metal  of  the 
magneto.  The  metal  screw  2,  which  holds  the  interrupter  in 
place,  carries  the  current  from  the  junction  of  the  armature 
windings  to  the  insulated  block  3  which  holds  the  platinum 
contact-screw  5.  The  movable  contact-screw  29  is  in  one  end 
of  the  interrupter  lever  7.  The  interrupter  lever  is  held  in  place 
by  a  pin  which  passes  through  it  at  the  angle  which  is  at  about 
the  middle  of  its  length.  This  pin  is  hidden  in  Fig.  227  behind 
a  small  flat  spring  that  holds  the  lever  on  the  pin.  The  inter- 
rupter lever  and  the  interrupter  disk  4,  on  which  the  lever  is 
mounted  by  means  of  the  pin  mentioned,  are  grounded  on  the 
metal  of  the  frame  of  the  magneto.  The  contact-points  are 
pressed  together  by  the  curved  spring  6,  one  end  of  which  is 
fastened  to  the  lever  and  the  other  end  to  the  interrupter  disk. 


(See  also  Figs.  226, 
227,  228,  and  Plates  I,  II,  III, 
and  IV.) 


276  ELECTRIC  IGNITION 


FIGS.  226  and  227. 

1.  Insulated  brass  plate  connected  to  one  side  of  condenser. 

2.  Screw   for   fastening   the   complete  interrupter   (contact-breaker)   in  place. 

Insulated  from  the  body  of  the  armature  and  from  the  interrupter. 

3.  Insulated  " stationary "  contact-piece.     Rotates  with  the  armature. 

4.  Disk  on  which  the  interrupter  parts  are  mounted.     Not  insulated. 

5.  Platinum  contact-screw  in  3. 

6.  Spring  for  pressing  interrupter  lever  contact-point  against  the  "stationary" 

contact-point. 

7.  Interrupter  (contact-breaker)  lever.    Not  insulated.. 

8.  Condenser. 

9.  Insulated  slip-ring  connected  to  the  high-tension  terminal  of  the  armature 

winding. 

10.  Carbon  brush  which  presses  against  slip-ring  9. 

11.  Brush-holder  for  10.     Of  insulating  material. 

12.  Connecting  bridge. 

13.  Carbon  brush  for  carrying  current  to  high-tension  distributer. 

14.  Rotor  of  distributer. 

15.  Distributing  brush  for  making  contact  with  the  stationary  contact-pieces  of 

the  distributer. 

16.  Stationary  insulating  piece  of  the  distributer. 

1 8.  Ends  of  high-tension  cables  for  making  connection  to  the  spark-plugs. 

19.  Fiber  rollers  against  which  the  end  of  the  interrupter  lever  strikes  so  as  to 

separate  the  contact  points  of  the  interrupter. 

20.  Arms  to  either  of  which  the  hand-control  for  regulating  (advancing  and  re- 

tarding) the  ignition  can  be  connected. 

21.  Dust-cover  above  armature. 

22.  Vulcanite  cover  for  distributer. 

23.  Three-arm  spider.     Not  insulated 

24.  Terminal  for  ground  wire  to  hand-switch.     Insulated. 

25.  Spring  for  holding  cap  26  in  place. 

26.  Brass  cover  cap  for  interrupter.     Insulated. 

27.  Brass  block  for  supporting  25. 

29.  Platinum  contact-screw  in  interrupter  lever  7. 

30.  Stop-screw  to  limit  the  rocking  movement  of  the  interrupter  casing  when 

advancing  or  retarding  the  ignition. 


INTERRUPTER  MAGNETOS  AND  JUMP-SPARK  IGNITION     277 

,16 


FIG.  226. 
Longitudinal  Section  of  Fig.  225. 


FIG.  227. 
Interrupter  End  of  Fig.  225  with  Covers  removed. 


278 


ELECTRIC  IGNITION 


INTERRUPTER  MAGNETOS  AND  JUMP-SPARK  IGNITION     279 

The  beginning  of  the  secondary  winding  of  the  armature  is 
connected  to  the  end  of  the  primary  winding.  The  high-tension 
terminal  of  the  secondary  winding  is  connected  to  the  insulated 
slip-ring  9  against  which  bears  the  carbon  brush  10.  This 
brush  is  carried  by  the  insulating  brush-holder  n.  The  carbon 
brush  10  is  connected  to  the  insulated  central  spindle  and 
carbon  brush  15  of  the  distributer  by  means  of  the  metal  con- 
nector 12  and  carbon  brush  13.  The  brush  15  is  carried  by  the 
insulating  material  14  of  the  distributer  rotor.  The  distribu- 
ter brush  15  makes  contact  successively  with  metal  contact- 
pieces  set  into  the  insulating  piece  16.  These  contact-pieces 
are  connected  to  terminals  into  which  fit  terminals  18  for  the 
wires  that  go  to  the  spark-plugs. 

When  the  magneto  armature  is  rotating,  together  with  the 
interrupter  disk  and  the  parts  attached  to  it,  the  end  of  the 
interrupter  lever  (right-hand  end  in  Fig.  227)  strikes  first  one  and 
then  the  other  of  two  fiber  rollers  19.  The  striking  of  the  end 
of  the  lever  against  the  rollers  causes  the  contact-points  of  the 
interrupter  to  separate  and  thus  break  the  primary  circuit. 
This  causes  a  spark  to  jump  at  the  spark-plug  with  whose 
terminal  the  distributer  is  in  contact  at  the  instant. 

The  part  carrying  the  fiber  rollers  19  can  be  rocked  slightly 
relative  to  the  frame  of  the  magneto,  in  order  to  advance  or 
retard  the  ignition.  Two  arms  20  are  provided  for  this  purpose. 
The  rocking  can  be  done  by  the  hand-control,  which  is  con- 
nected to  one  of  the  arms  20. 

For  cutting  out  ignition,  the  terminal  24  is  provided.  This 
terminal  is  insulated  and  connected  to  the  insulated  junction  of 
the  primary  and  secondary  windings  by  means  of  the  spring 
25  that  presses  against  the  insulated  metal  cap  26.  The  latter 
carries  a  spring-mounted  carbon  button,  or  brush,  which  bears 
against  the  outer  end  of  the  metal  screw  2.  The  screw  is  con- 
nected to  the  junction  of  the  two  windings,  as  has  been  stated. 
If  a  wire  is  led  from  the  terminal  24  to  one  side  of  a  hand  switch, 
whose  other  side  is  grounded,  then  the  closing  of  the  switch 
will  keep  the  primary  circuit  of  the  magneto  permanently  closed 
and  thus  prevent  sparking  at  the  spark-plugs.  Under  this 


280  ELECTRIC  IGNITION 


PLATE  I. 

Magnets  and  End  Plates. 

30.  Stop  screw  for  timing-lever  20. 

31.  Magnet  casing,  pole-shoes,  and  base-plate  (only  2  double  magnets  for  "DR3," 

"D.R.4"  and  2  single  magnets  for  "DR6,"  not  3  as  shown). 

32.  Long  magnet-screws. 

33.  Short  magnet-screws. 

34.  Holding  down  screws  for  pole-shoes  to  base-plate. 

35.  Front  end-plate. 

36.  Long  screws  for  front  end-plate. 

37.  Short  screws  for  front  end-plate. 

38a.  Oil  cover  (with  arrow  <—)  for  front  end-plate. 

38b.  Oil  cover  (with  arrow  — >)  for  front  end-plate. 

39.  Oil  cover  screw  for  front  end-plate. 

40.  Spiral  spring  for  oil  cover  screws  39  and  50. 

41.  Ball-race  collar  for  ball  bearings. 

42.  Rear  end-plate  without  screws. 

43.  Screw  for  rear  end-plate. 

44.  Screw  for  bearing  flange  53  and  56. 

45.  Rear  end-plate  cover. 

46.  Long  screws  for  45. 

47.  Short  screws  for  45. 

48.  Left-hand  oil  lid  for  45. 

49.  Right-hand  oil  lid  for  45. 

50.  Oil-lid  screw  for  45. 

51.  Paper  strip  for  ball  race  in  both  end-plates. 

52.  Paper  washer  for  ball  race  in  both  end-plates. 

53.  Flange  with  oil  lid  and  ball-race  collar  for  two  ball  bearings. 

54.  Ball-race  collar  for  flange  53. 

55.  Paper  for  ball-race  collar  54. 

56.  Flange  with  slide  bearing,  oil  wick  and  oil  cover. 

57.  Oil-wick  screw  for  flange  56  with  wick  spring  and  packing  washer. 

58.  Wick  screw  only  without  parts. 

59.  Felt  wick  and  spiral  spring. 

60.  Leather  washer  for  wick  screw. 

61.  Oil  cover  for  flange  53  and  56  for  type  "DR4." 

62.  Oil-cover  screw  for  flange  53  and  56  for  type  "DR4." 

63.  Spiral  spring  for  oil-cover  screw  62. 

64a.  Oil  cover  left  upperside  on  rear  end-plate  for  type  "  DR6." 

64b.  Oil  cover  right  upperside  on  rear  end  plate  for  type  "DR6." 

65.  Screw  for  oil  cover  64a  and  64b. 


INTERRUPTER  MAGNETOS  AND  JUMP-SPARK   IGNITION     281 


43 


PLATE  I.    Parts  of  Fig.  225. 


282  ELECTRIC  IGNITION 

PLATE  II. 
Armature  and  Contact  Breaker. 

1.  Rear  condenser-plate  with  insulator  78. 

2.  Contact-breaker  screw. 

3a.   Platinum-screw  block  for  anti-clockwise  machines. 
3b.   Platinum-screw  block  for  clockwise  machines. 
4a.   Complete  contact-breaker  for  anti-clockwise  machines. 
4_b.   Complete  contact-breaker  for  clockwise  machines. 

5.  Long  platinum  screw. 

6.  Contact-breaker  spring. 

ya.   Contact-breaker  bell-crank  lever  for  anti-clockwise  machines, 
yb.   Contact-breaker  bell-crank  lever  for  clockwise  machines. 

8.  Condenser  with  connections  and  paper  insulation  binding. 

9.  Slip-ring  for  armature. 
29.   Short  platinum  screw. 

66.  Complete  armature  with  pinion,  slip-ring,  condenser,  and  two  ball-race  rings, 

without  ball-race  collar. 

67.  Front  armature-disk. 

68.  Fastening  screw  for  67. 

69.  Rear  end  insulation  for  slip-ring. 

70.  Front  insulation  for  slip-ring. 

71.  Washer  for  shaft  cone  f". 

72.  Nut  for  shaft  cone  f  ". 

73.  Rear  armature-disk. 

74.  Fastening  screw  for  rear  armature-disk. 
76.  Ebonite  insulating  plate  for  the  condenser. 

78.  Insulation  button. 

79.  Insulation  silk. 

80.  Front  condenser-plate. 

81.  Condenser  screw. 

82.  Small  hexagon  nut  for  the  condenser. 

83.  Washer  for  82. 

84.  Insulating  strip  for  condenser. 

85.  Small  gear  wheel  on  armature  disk. 

86.  Fastening  screw  for  gear  wheel  85. 

87.  Inside  ball-race  ring  for  the  ball  bearings. 

88.  Cage  for  balls  suitable  for  both  ball  bearings. 

89.  Felt  disk  for  packing  the  one  end  of  the  armature. 

90.  Screw  for  contact-breaker  spring. 

91.  Washer  for  90. 

92.  Nut  for  long  platinum  screw. 

93.  Insulation  for  contact-piece  on  contact-breaker. 

94.  Insulation  bush  for  93. 

95.  Screw  for  contact-piece  on  contact-breaker. 

96.  Insulation  bush  for  center  of  contact-breaker  disk. 

97.  Flat  spring  pressing  on  to  bell-crank  lever. 

98.  Washer  for  97. 

99.  Carbon  brush  for  the  contact-breaker. 
100.   Spiral  spring  for  99. 


INTERRUPTER   MAGNETOS   AND  JUMP-SPARK   IGNITION     283 


85     73 


78 


O82 


83® 


PLATE  II.    Parts  of  Fig.  225. 


284  ELECTRIC  IGNITION 

PLATE  III. 
Current  Collector,  Distributer,  and  Timing  Lever. 

10.  Carbon  brush  with  spiral  spring  for  carbon-holder  n. 

11.  Carbon-holder  without  carbon  and  spiral  spring, 
na.  Carbon-holder  with  carbon  and  spring. 

12.  Complete  connecting  bridge  with  carbon-holder  (brass)  together  with  in- 

sulation piece  and  lock  spring. 

13.  Carbon  with  spring  for  brass  holder  on  connecting  bridge  12. 

14.  Rotating  distributer  piece  without  carbon  and  spring. 
i4a.   Rotating  distributer  piece  with  carbon  and  spring. 

15.  Carbon  with  spiral  spring  for  rotating  distributer  piece. 

1 6.  Distributer  disk  without  screws. 

18.  High-tension  cable  800  mm.  long  with  terminal,  brass  plug  and  insulating 

sleeve. 

i8a.  Brass  plug  with  ebonite  insulating  sleeve  only  for  cable  18. 

19.  Fiber  rollers  for  advance  and  retard  lever  20. 

20.  Complete  timing  lever  with  fiber  rollers. 

21.  Dust-cover  only  with  cap  for  safety  gap. 

22.  Ebonite  cover  for  distributing  disk  16. 

23.  Complete  triangular  clamp  for  the  distributer  disk  together  with  brass  con- 

necting piece  and  spring. 

23a.  Clamp  only  without  parts. 

24.  Rundled  nut  for  switch  wire  (short  circuit). 

25.  Spring  for  brass  cap  26. 

26.  Brass  cap  for  timing  lever  20  together  with  carbon  and  spring. 

27.  Brass  block  for  spring  25. 

28.  Fixing  or  head  bolt  for  fixing  spring  25. 
30.  Stop  screw  for  timing  lever  20. 

101.  Bell-shaped  insulation  piece  on  the  connecting  bridge  12. 

102.  Spiral  spring  for  carbon  13. 

103.  Steatite  cover  for  safety-gap  together  with  electrode  104. 

104.  Electrode  of  steatite  cover  for  spark-gap. 

105.  Screw  for  fixing  the  dust-cover  21. 

106.  Spiral  spring  for  carbon  10. 

107.  Insulating  ring  for  brass  cap  26. 

108.  Cover  for  fiber  rollers  in  advance  and  retard  lever  20  together  with  steel 

stud  109. 

109.  Steel  stud  for  fiber  rollers  in  timing  lever  20. 
no.   Fixing  screw  for  cover  108. 

in.  Top  screw  for  terminal  block  and  clamp. 

112.  Bottom  screw  for  terminal  block  and  clamp. 

113.  Spiral  spring  for  carbon  15. 

114.  Insulating  plate  for  connecting  piece  27. 

115.  Insulating  bush  for  connecting  piece  27. 

116.  Fixing  screw  for  connecting  piece  27. 

117.  Washer  for  spring  25. 

1 1 8.  Complete  distributing  gear  wheel  together  with  shaft  and  catch  plate. 

119.  Fiber  ring  riveted  on  the  distributing  gear  wheel  (former  execution). 

120.  Shaft  for  distributer  gear  wheel. 

121.  Fixing  screw  for  shaft  of  distributer  gear  wheel. 

122.  Inside  ball-race  ring  for  the  ball  bearings  fixed  to  shaft  120. 

123.  Cage  with  steel  balls. 

1 24.  Spring  ring  at  front  end  of  the  shaft  1 20. 

125.  Ebonite  catch-plate. 

126.  Fastening  screw  for  catch-plate  125. 


INTERRUPTER  MAGNETOS  AND  JUMP-SPARK   IGNITION      285 


101 


PLATE  III.    Parts  of  Fig.  225. 


286  ELECTRIC  IGNITION 


PLATE  IV. 

For  Newer  Designs. 

1  a.   Rear  condenser-plate  for  condenser  8a. 

2  a.   Contact-breaker  screw.     (Only  suitable  for  armature  with  rear  shaft  and 

disk  73a.) 
8a.   Condenser  with  connection  and  connecting  plate  la.     (Only  suitable  for 

armature  shaft  and  disk  73a.) 
gc.   Slip-ring  in  one  piece,  without  thread.     (Only  suitable  for  armature  shaft 

and  disk  67a.) 
nb.   Carbon-holder  without  thread,  with  spiral  spring  and  carbon.     (Only  suitable 

for  dust-cover  21  a.) 
nc.   Carbon-holder   without   thread,    minus   spiral   spring   and   carbon.     (Only 

suitable  for  dust  cover  2ia,.) 
2ia.   Dust-cover  with  ball  clip  fastening,  without  any  other  parts.     (Carbon-holder 

minus  thread  No.  nb  is  suitable  for  this  cover.) 
2ib.  Dust-cover  with  ball  clip  fastening,  without  any  other  parts.     (Carbon-holder 

with  thread  1 1  on  illustration  1 1 1  is  suitable  for  this  cover.) 
42a.  Rear  end-plate  with  center  lubrication. 

45b.   Rear  end-plate  cover  for  center  lubrication.     (Only  suitable  for  rear  end- 
plate  42a.) 

47.   Short  screw  for  4$b. 
67a.   Front  armature  shaft  and  disk  minus  thread  on  shaft  (slip-ring  gc  is  suitable 

for  this). 
73a.   Rear  armature  disk  with  protecting  of  condenser. 

210.  Bent  steel  washer  for  fastening  slip-ring  gc. 

211.  Brass  nut  on  dust-cover  2ia  for  fastening  carbon-holder  nb. 

212.  Body  carbon  with  cable  for  base  plate  of  magnet  casing. 

213.  Screw  for  fastening  body  washer  to  base  plate  of  magnet  casing. 

214.  Washer  for  screw  213. 

215.  Flat  spring  to  keep  body  carbon  212  in  position. 

216.  Fastening  screw  for  flat  spring  215. 

217.  Washer  for  screw  216. 

218.  Strengthening  spring  for  bell-crank  lever  7a  and  7b. 

219.  Strengthening  spring  on  projecting  brass  lug  of  the  contact-breaker  disk  4c. 

220.  Oil-paper  strip  to  fix  condenser  8a  on  rear  armature  shaft  and  disk  73a. 

221.  Felt  strip  to  fix  condenser  8a  on  rear  armature  shaft  and  disk  73a. 

222.  Linen  strip  to  insulate  condenser  8a. 

223.  Pressed  linen  insulation  for  condenser  8a. 

224.  Fastening  screw  for  condenser  8a. 

225.  Insulating  bush  on  connecting  plate  on  condenser  8a. 


INTERRUPTER  MAGNETOS   AND   JUMP-SPARK   IGNITION       287 


PLATE  IV.     Parts  of  Fig.  225.. 


288 


ELECTRIC  IGNITION 


INTERRUPTER  MAGNETOS    AND  JUMP-SPARK  IGNITION     289 


Cf 


FIG.  230. 
Interrupter  for  Fig.  229. 


FIGS.  229,  230,  and  231. 

A.  Timing  lever  and  cam  lobes. 

B.  Clip-spring  for  holding  timer  cover  in  place. 

C.  Steel  disk  of  interrupter. 

C  i.  Slip-ring  for  the  short-circuiting  cut-out. 

D.  Interrupter  arm. 

d.  Barrel  of  interrupter,  bronze. 

E.  Spring  on  which  the  interrupter  arm  is  mounted. 

e.  Centering  disk,  steel. 

F.  Socket  for  hinge  pin  of  interrupter  lever, 
f.  Contact-points  of  interrupter. 

G.  Nut  for  holding  the  interrupter  in  place. 
H.  Insulated  stud. 

h.  Cover  plate  of  condenser. 

I.  Brush-holder  and  terminal  for  the  short-circuiting  cut-out. 

J,  J.  Cam  lobes. 

P.  Distributer  cover. 

R.  Clip- spring  for  holding  distributer  cover  in  place. 

S.  Distributer  plate,  of  insulating  material. 

T.  Distributer  brush, 

t.  Distributer  shaft. 


2QO 


ELECTRIC  IGNITION 


condition  there  can  be  no  sudden  interruption  of  the  primary 
current  by  the  action  of  the  interrupter.  The  variations  of  the 
primary  current  in  the  permanently  closed  circuit  will  not  pro- 
duce a  spark  at  the  spark-plugs. 

A  safety  spark-gap  is  provided  in  the  secondary  circuit.  It 
is  shown  in  Fig.  226  between  the  insulated  connecting  strip  12 
and  the  grounded  dust-cover  21  which  is  just  over  the  armature. 
One  spark-point  of  the  safety-gap  is  connected  to  the  insulated 


FIG.  231. 
Device  for  Setting  the  Interrupter  of  Fig.  229. 

conductor  12;  the  other  spark-point  is  connected  to  the  dust-cap. 
The  safety-gap  is  enclosed  by  a  short,  tubular  piece  of  metal 
and  a  steatite  cap  on  the  top  of  the  short  tube,  together  with  a 
porton  of  the  dust-cap.  The  tubular  piece  has  several  holes 
leading  to  the  atmosphere.  These  holes  have  fine-mesh  wire 
gauze  over  them  to  prevent  the  ignition  of  gasoline  vapor  out- 
side of  the  safety-gap  inclosure,  in  case  such  vapor  should 
happen  to  gather  around  the  magneto  to  an  amount  that  makes 
a  combustible  mixture  with  air. 

"Ground"  connection  between  the  body  of  the  armature  and 
the  frame  of  the  magneto  is  made  certain  by  a  carbon  brush 


INTERRUPTER  MAGNETOS  AND  JUMP-SPARK  IGNITION     291 

which  presses  against  the  metal  of  the  armature.  This  brush 
is  shown  just  beneath  the  casing  of  the  condenser  in  Fig.  226. 
It  is  connected  to  the  base-plate  of  the  magneto  by  a  short 
electric  cable  that  is  fastened  to  the  base-plate  by  a  screw.  A 
flat  spring  presses  against  the  outer  end  of  the  brush  to  keep  the 
latter  in  contact  with  the  armature.  The  brush  with  the  at- 
tached cable  is  shown  at  212  in  Plate  IV,  together  with  the 
other  parts,  213,  214,  215,  216,  and  217,  for  making  the  ground 
connection.  In  some  magnetos,  the  bearings  in  which  the  arma- 
ture spindle  rotates  are  depended  upon  to  make  the  ground  con- 
nection of  the  armature  to  the  frame  of  the  magneto,  but  this 
is  not  an  entirely  reliable  means,  for  oil  and  dirt  in  the  bearings 
may  at  times  cause  imperfect  contact  between  the  spindle  and 
the  supporting  part  of  the  bearing. 

183.  U.  &  H.  (Unterberg  &  Helmle)  Magneto  with  Rotary 
Double-wound  Shuttle  Armature.  —  In  Fig.  229  this  machine  is 
shown  with  some  of  the  parts  removed  to  make  clear  the  con- 
struction. The  interrupter  is  also  shown  separately  in  Fig.  230. 

The  electric  connections  of  this  magneto  are  the  same  in  effect 
as  those  shown  in  Fig.  224. 

The  interrupter  is  of  unusual  design.  Referring  to  Fig.  230, 
the  contact-points  are  shown  at  /.  The  stationary  contact- 
point  is  connected  to  the  electrically  insulated  steel  disk  C, 
upon  which  the  slip-ring  Ci  is  mounted  and  electrically  con- 
nected to  it. 

The  movable  contact-point  is  attached  to  an  interrupter  arm 
D  which  is  mounted  on  an  elastic  member  E  that  is  bent  back 
upon  itself  so  as  to  form  a  spring  of  suitable  form  to  carry  the 
interrupter  arm.  E  is  fastened  between  a  steel  centering  disk  e 
and  a  cylindrical  bronze  part  or  barrel  d.  An  insulated  socket 
F  is  provided  for  the  rounded  end  of  a  hinge  pin  in  the  inter- 
rupter lever  D. 

The  interrupter  lever  D,  the  elastic  member  E,  and  the  parts 
e  and  d  are  electrically  connected  together.  When  the  inter- 
rupter is  in  place  on  the  magneto  these  parts  make  connection 
with  the  grounded  side  of  the  armature. 

The  curved  portion  of  the  interrupter  arm  which  is  shown 


2Q2 


ELECTRIC  IGNITION 


PLATE  V.    Parts  of  Fig.  229. 


INTERRUPTER  MAGNETOS  AND  JUMP-SPARK   IGNITION      293 

projecting  at  the  upper  part  of  the  illustrations  strikes  against 
the  lobes  of  a  cam  as  the  armature  rotates,  so  as  to  move  the 
lever  back  and  separate  the  con  tact- points.  These  lobes  are 
shown  at  /  and  /  in  Fig.  229.  They  are  attached  to  the  cam- 
piece  A,  of  which  the  timing  lever  for  connecting  to  the  spark 
control  is  a  part. 

When  the  interrupter  is  in  place  the  centering  disk  e  bears 
against  one  of  the  cover-plates  h  of  the  condenser  which  lies 
between  the  interrupter  and  the  winding  of  the  armature. 

The  interrupter  is  held  in  place  by  a  nut  G  which  screws  on 
the  insulated  stud  H,  that  is  connected  to  the  junction  of  the 
primary  and  secondary  windings  of  the  armature.  The  insulated 
disk  C,  bronze  slip-ring  Ci,  and  the  stationary  interrupter 
point  are  thus  connected  to  the  junction  of  the  two  windings. 

The  beginning  of  the  primary  coil  of  the  armature  winding  is 
grounded  to  the  armature  core.  The  end  of  the  secondary 
winding  is  connected  to  a  slip-ring  at  the  end  of  the  armature 
next  to  the  driving  gear.  This  slip-ring  is  shown  in  Plate  V. 

The  high-tension  current  is  carried  from  this  slip-ring  through 
a  brush  and  suitable  connections  to  the  distributer  brush  T, 
which  is  rotated  in  the  usual  manner  by  a  pair  of  gears  that 
connect  the  shaft  which  drives  /  and  its  brush-holder  for  T  to  the 
armature  shaft.  The  brush  and  brush-holder  are  shown  drawn 
partly  out  from  the  recess  in  which  they  properly  belong.  The 
distributer  plate  5  is  of  insulating  material  and  has  four  contact- 
pieces  against  which  the  distributer  brush  T  rubs  successively 
during  its  rotation. 

When  in  proper  position  the  interrupter  rotor  is  protected  by 
the  cover  P  which  is  held  in  place  by  the  clip  R. 

The  cam-piece  A-J  fits  into  the  cylindrical  housing  on  the 
interrupter  so  as  to  bring  the  lobes  /  into  the  proper  position  for 
the  curved  end  of  the  interrupter  arm  D  to  strike  them.  The 
rocking  movement  which  can  be  given  to  the  cam-lobes  in  order 
to  advance  and  retard  the  ignition,  is  limited  by  a  small  stop 
shown  in  the  inside  of  the  cylindrical  housing  in  the  right-hand 
lower  part.  The  rocking  part  A-J  is  held  in  place  by  the 
clip  B. 


2 94  ELECTRIC  IGNITION 

The  brush-holder  /  fits  into  the  threaded  opening  shown  at 
the  left-hand  upper  part  of  the  interrupter  housing.  The  brush 
in  this  holder  bears  against  the  slip-ring  Ci.  This  brush-holder 
forms  the  ground  terminal  which  is  to  be  connected  to  a  switch 
that  remains  open  while  the  magneto  is  operating,  but  is  closed 
in  order  to  stop  the  operation  of  the  magneto.  Connecting  the 
ground  terminal  to  ground  in  the  manner  just  stated  short- 
circuits  the  primary  winding  of  the  magneto. 

A  safety  spark-gap  is  provided  between  one  of  the  high- 
tension  connections  and  the  grounded  dust-plate  which  goes 
just  above  the  armature.  The  safety-gap  is  inclosed  by  porce- 
lain and  metal  walls,  the  latter  being  perforated,  so  as  to  form 
openings  through  which  a  spark  passing  between  the  points  can 
be  seen.  The  openings  of  the  metal  are  provided  with  mica 
windows  for  the  exclusion  of  vapor  and  dust. 

A  convenient  manner  of  holding  the  interrupter  in  proper 
position  during  the  process  of  timing  the  magneto  is  by  means 
of  the  pin  shown  in  Fig.  231.  This  pin  passes  through  a  small 
hole  in  the  cam-piece  A  and  enters  a  hole  Z  in  the  interrupter. 
The  hole  in  the  part  A  is  closed  by  a  screw  during  the  operation 
of  the  magneto. 

This  magneto,  in  some  of  its  types,  is  provided  with  a  start- 
ing device  which  enables  a  motor  to  be  started  on  magneto  spark 
without  the  necessity  of  cranking,  or  otherwise  rotating  the 
motor,  at  a  speed  any  higher  than  is  necessary  for  battery 
ignition  with  a  trembler  spark-coil.  Briefly,  the  magneto  is 
driven  by  means  of  a  device  containing  a  stout  spring  and  a 
loose  ball.  When  the  driving  mechanism  is  rotated  slowly,  the 
ball  locks  the  armature  so  that  it  cannot  rotate  until  after  the 
spring  has  been  wound  up  to  some  extent.  The  ball  then  strikes 
a  part  which  throws  it  out  of  its  locking  position,  and  the  arma- 
ture is  rapidly  rotated  by  the  spring  far  enough  to  produce  a 
strong  ignition  spark.  As  soon  as  the  motor  starts  on  its  own 
power,  the  speed  of  the  mechanism  that  drives  the  magneto  is 
high  enough  to  prevent  the  ball  from  dropping  into  its  locking 
position,  and  the  armature  is  then  driven  continuously  at  the 
speed  of  the  driving  mechanism. 


INTERRUPTER  MAGNETOS   AND  JUMP-SPARK  IGNITION     295 

184.  Remy  Magneto  with  Stationary  Armature  and  Rotary 
Inductor.  —  Fig.  232  is  a  full  view  of  the  magneto.  Fig.  233  is  a 
photographic  end  view,  and  A  of  Fig.  236  is  a  line-drawing  end 
view;  the  covers  of  the  interrupter  and  distributer  are  removed 


FIG.  232.     (See  also  Figs.  233,  234,  235,  236,  and  256.) 

Remy  Magneto  with  Stationary  Single-wound  Armature  and  Rotary  Inductor. 
Remy  Electric  Company,  Anderson,  Indiana. 

in  both  of  these  views.     Sectional  views  are  shown  in  Figs,  234 
and  236.     The  armature  winding  and  the  inductor  are  shown  in 
Fig.  235. 
The  armature  winding  i  is  a  single-wound  circular  coil.     It  has 


296 


ELECTRIC  IGNITION 


several  turns  of  rather  coarse  insulated  wire.  The  coil  encircles 
an  enlargement  of  the  inductor  shaft  2,  which  has  fastened  to 
it  (by  pins)  two  forged  steel  arms,  or  wings,  3  and  4.  These 


- 

FIG.  233. 
Interrupter  End  of  Fig.  232  with  Cover-Plates  removed. 

wings,  together  with  the  enlarged  portion  of  the  shaft,  form  the 
rotary  inductor  of  the  magneto.  The  form  and  disposition  of 
the  wings  can  be  seen  by  examining  Figs.  234,  235,  and  236. 


INTERRUPTER  MAGNETOS  AND  JUMP-SPARK  IGNITION     297 

The  wings  extend  in  opposite  directions  from  the  shaft,  and  the 
outer  end  of  each  wing  is  crowned  cylindrically  to  conform  to 
the  concave  surfaces  of  the  magnet-poles  between  which  they 
revolve.  One  of  the  magnet-poles  is  shown  in  section  at  5, 
Fig.  234.  The  armature  coil  is  partly  embedded  in  the  magnet 


2.0 


FIG.  234. 
Longitudinal  Section  of  Fig.  232. 


poles.  The  magnets  6  are  of  the  ordinary  U-shaped  compound 
type.  One  end  of  the  armature  coil  is  connected  to  the 
grounded  terminal  7 ;  the  other  end  is  connected  to  the  insulated 
terminal  8,  from  which,  in  an  ignition  system,  a  wire  leads  to  a 
non-trembler  spark-coil,  or  to  a  switch  connected  to  the  spark- 
coil. 

Each  revolution  of  the  inductor  produces  two  impulses  of 
alternating  current  in  the  armature  coil.  The  direction  of  mag- 
netic flux  through  the  inductor  during  each  revolution  is  first 


298  ELECTRIC  IGNITION 

from  the  north  pole  of  the  magnets  to  and  through  the  inductor 
wing  3,  thence  through  the  enlargement  of  the  shaft  and  on 
through  the  wing  4  to  the  south  pole  of  the  magnets.  After 
half  a  revolution  of  the  inductor,  the  magnetic  flux  is  from  the 
north  pole  of  the  magnets  to  the  inductor  wing  4,  enlarged  portion 
of  the  shaft,  wing  3,  and  the  south  pole  of  the  magnets.  The 


FIG.  235. 
Rotary  Inductor  and  Stationary  Armature  Coil  for  Fig.  232. 

magnetic  flux  is  thus  reversed  in  its  direction  of  flow  through  the 
armature  coil  twice  each  revolution. 

The  interrupter  rocker-arm,  or  rocker-lever,  9,  is  kept  pressed 
against  a  two-lobed  cam  10  by  means  of  a  coiled  compression 
spring  ii.  The  cam  is  fastened  to  the  inductor  shaft  and  rotates 
with  it.  The  rocker-lever  has  two  arms,  to  one  of  which  is  fas- 
tened the  blade-spring  12.  The  movable  contact-point  of  the 


INTERRUPTER  MAGNETOS   AND  JUMP-SPARK  IGNITION     299 


FIGS.  232,  233,  234,  235,  and  236. 

1.  Armature  Coil. 

2.  Inductor  shaft. 

,  4.  Wings  of  Inductor. 

5.  Magnet  pole. 

6.  Magnets. 

7.  Grounded  terminal  of  armature  coil. 

8.  Insulated  terminal  of  armature  coil. 

9.  Interrupter  rocker-lever. 

10.  Interrupter  cam. 

11.  Compression  spring. 

12.  Blade  springs. 

13.  Insulated  terminal  of  interrupter. 

14.  Metallic  part  of  distributer  rotor,  insulated. 

15.  Central  terminal  of  distributer. 

16.  Central  contact  carbon  of  distributer. 

17.  Distributer  shaft. 

18.  Adjusting  screw  of  interrupter  contacts. 

19.  Hammer  end  of  interrupter  lever. 

20.  Arm  for  rocking  the  interrupter. 


300 


ELECTRIC  IGNITION 


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INTERRUPTER  MAGNETOS   AND  JUMP-SPARK  IGNITION     301 

interrupter  is  fastened  to  the  free  end  of  the  blade-spring.  When 
the  cam  is  in  the  position  shown  in  Fig.  236,  the  movable  con- 
tact-point is  pressed  against  its  mating  stationary  contact-point, 
which  is  an  extension  of  the  insulated  terminal  13.  As  the  cam 
rotates,  it  forces  the  rocker-lever  back  against  the  resistance  of 
the  coiled  compression  spring  and  causes  separation  of  the  con- 
tact-points so  as  to  break  the  armature  circuit.  Quick  separa- 
tion of  the  contact-points  is  secured  by  means  of  the  striking  end 

19  of  the  interrupter  lever. 

The  stationary  contact-point  can  be  adjusted  by  turning  the 
screw  in  which  it  is  mounted.  A  knurled  piece  of  insulating 
material  18  is  provided  for  making  this  adjustment.  The  arm 

20  is  provided  for  rocking  the  entire  interrupter  by  hand  to  ad- 
vance and  retard  the  time  of  ignition. 

The  distributer  has  high-tension  current  brought  to  its  insu- 
lated metallic  rotor  14  from  the  spark-coil  by  means  of  a  wire 
connected  to  the  terminal  15.  The  latter  is  connected  to  the 
distributer  rotor  by  the  carbon  contact  brush  16.  The  rotor 
of  the  distributer  is  rigidly  mounted  on  the  shaft  17,  which  is 
driven  by  gears  connecting  it  to  the  inductor  shaft  as  shown. 
The  distributer  rotor  directs  the  high-tension  current  succes- 
sively to  the  four  terminals  shown  at  the  upper  part  of  the  illus- 
trations. In  a  complete  ignition  system,  these  terminals  are 
connected  to  the  spark-plugs  that  produce  ignition  in  the 
motor. 

185.  Effect  of  Advance  and  Retard  on  the  Strength  of  the 
Ignition  Spark.  —  One  much-used  method  of  varying  the  instant 
of  ignition  (of  advancing  and  retarding  the  spark)  is  to  rock  the 
entire  interrupter  relative  to  the  rotor  (armature  or  inductor)  of 
the  magneto.  If  the  interrupter  is  rocked  in  the  direction 
opposite  the  rotation  of  the  rotor,  the  ignition  spark  is  thereby 
advanced;  or  if  the  interrupter  is  rocked  in  the  direction  of 
rotation  of  the  rotor,  the  spark  is  thereby  retarded. 

It  has  already  been  pointed  out  that  the  alternating  electric 
current  generated  in  the  low-tension  winding  of  a  shuttle-wound 
armature  as  it  rotates  between  magnet-poles  is  at  or  near  its 
maximum  value  during  only  a  very  small  portion  of  a  revolution 


302  ELECTRIC  IGNITION 

of  the  armature  or  inductor.  The  same  is  true  relative  to  other 
types  of  armatures  in  a  bipolar  alternating-current  magneto. 
Therefore  if  the  interrupter  is  rocked  relative  to  the  magnet- 
poles  as  well  as  relative  to  the  armature,  the  primary  current 
will  be  smaller  at  the  instant  of  its  interruption,  when  the  ignition 
is  either  fully  advanced  or  fully  retarded,  than  when  the  inter- 
rupter is  in  an  intermediate  position.  The  result  is  that  a 
weaker  spark  is  obtained  for  ignition  when  the  interrupter  is 
advanced  or  retarded  than  when  it  is  at  an  intermediate  posi- 
tion. This  weakening  of  spark  strength  is  not  so  great,  however, 
but  that  numerous  excellent  magnetos  are  in  operation  in  which 
the  advance  and  retard  of  the  spark  is  obtained  by  rocking  the 
entire  interrupter  relative  to  both  the  rotor  and  the  magnet- 
poles,  the  latter  remaining  stationary  relative  to  the  frame  on 
which  the  magneto  is  mounted. 

On  the  other  hand,  various  methods  have  been  adopted  in 
connection  with  interrupter  magnetos,  to  secure  an  ignition 
spark  of  the  same  length  for  all  settings  of  the  ignition,  from  full 
advance  to  full  retard.  Of  these  methods,  the  chief  ones  are: 

Rocking  extensions  of  the  magneto  poles,  to  rock  with  the 
interrupter; 

Rocking  magnets; 

Shaft  couplings  in  which  one  part  can  be  rotated  by  the  spark- 
control  mechanism,  through  a  portion  of  a  revolution  relative 
to  the  other  part; 

Alternately  charged  and  discharged  condenser. 

These  methods  are  described  in  the  following  part  of  this 
chapter,  either  separately  or  in  connection  with  a  magneto. 

186.  Charged-and-Discharged  Condenser  Ignition  System.  - 
The  magneto  for  this  system  has  a  condenser  of  comparatively 
large  capacity.  The  armature  has  a  low-tension  winding  only 
and  there  is  a  non-trembler  spark-coil  separate  from  the  arma- 
ture. The  magneto  has  two  devices  of  the  nature  of  an  inter- 
rupter, one  of  which  will  be  called  a  circuit-closer,  and  the  other 
an  interrupter.  An  alternating  current  is  generated. 

During  the  operation  of  the  magneto,  the  condenser  is  first 


INTERRUPTER  MAGNETOS  AND   JUMP-SPARK  IGNITION     303 

connected  to  the  armature  of  the  magneto  through  the  closed 
interrupter  until  the  condenser  becomes  charged.  The  inter- 
rupter then  breaks  the  connection  between  the  armature  and 
condenser  at  about  the  instant  of  maximum  voltage  in  the 
armature,  thus  leaving  the  condenser  charged  on  open  circuit. 
Then,  at  the  instant  of  ignition,  the  circuit-closer  closes  the  cir- 
cuit between  the  spark-coil  and  the  condenser.  The  condenser 
discharges  through  the  primary  of  the  spark-coil  as  soon  as  the 
condenser- transformer  circuit  is  closed.  The  discharge  current 
from  the  condenser  acts  to  produce  an  ignition  spark  at  the 
spark-plug.  Two  ignition  sparks  per  revolution  of  the  armature 
are  produced  when  the  latter  is  of  the  ordinary  shuttle-wound 
type  and  rotates  between  bipolar  magnets. 

The  breaking  of  the  armature-condenser  circuit  always  occurs 
at  the  same  instant  with  regard  to  the  position  of  the  armature 
relative  to  the  magnet-poles.  The  condenser,  therefore,  always 
receives  the  same  amount  of  charge,  at  a  given  speed  of  rotation 
of  the  armature,  regardless  of  the  time  of  ignition  relative  to 
advance  and  retard.  Consequently,  the  condenser  sends  the 
same  amount  of  current  through  the  transformer  whatever  the 
time  of  ignition,  at  any  given  rotative  speed  of  the  armature. 
The  strength,  or  hotness,  of  the  ignition  spark  is  the  same  what- 
ever the  time  of  ignition.  A  hotter  spark  is  produced  at  high 
speeds  of  the  armature  than  at  low  speeds,  which  is  true  of  all 
magnetos. 

187.  Shaft  Couplings  for  Advancing  and  Retarding  the  Igni- 
tion. —  A  form  of  coupling  that  is  quite  commonly  used  for  this 
purpose  consists  of  one  or  two  pieces  in  which  a  helical  slot  or 
groove  is  cut,  and  another  part  having  a  key  or  pin  which  fits 
into  the  groove.  By  moving  one  part  longitudinally  relative  to 
the  other,  rotation  of  the  one  relative  to  the  other  is  caused  to  a 
limited  extent.  Thus,  if  the  driving  shaft  is  held  from  rotating, 
then  sliding  one  part  of  the  coupling  along  the  other  will  cause 
the  armature  of  the  magneto  to  rotate  through  part  of  a  revolu- 
tion. If  the  interrupter  is  fixed  in  position  (not  constructed  so 
as  to  rock)  the  instant  of  ignition  will  be  changed  by  this  move- 
ment of  the  armature.  Moving  the  coupling  so  that  the  armature 


3°4 


ELECTRIC  IGNITION 


INTERRUPTER  MAGNETOS  AND  JUMP-SPARK  IGNITION     305 

is  thereby  rotated  through  part  of  a  revolution  relative  to  the 
driving  shaft,  in  the  direction  that  they  run,  advances  the  spark, 
and  vice  versa.  Since  the  interrupter  is  not  rocked  relative  to 
the  magnet-poles,  and  is  operated  from  the  armature  shaft,  the 
armature  is  always  in  the  same  position  relative  to  the  magnet- 
poles  at  the  instant  that  the  interrupter  breaks  the  primary 
circuit  to  produce  a  spark.  A  spark  of  uniform  strength  is 
therefore  produced  for  all  settings  of  the  ignition  from  full  advance 
to  full  retard,  at  any  given  speed  of  the  armature. 

One  form  of  helically  slotted  driving  coupling  is  shown  both 
in  detail  and  on  the  magneto  in  Fig.  237. 

The  smaller  slotted  tubular  part  is  fastened  rigidly  to  the 
armature  shaft,  and  the  larger  slotted  tube  fits  loosely  over  the 
smaller  tube.  The  ring  with  two  inward  projecting  pins  fits 
over  the  larger  tube,  and  the  pins  project  through  the  slots  in 
both  tubes,  thus  preventing  the  rotation  of  one  relative  to  the 
other.  The  ring  is  held  in  place  longitudinally  by  the  collar 
bearing  shown  in  two  parts  at  the  upper  portion  of  Fig.  237.  The 
collar  bearing  has  two  trunnion  pins  to  which  the  timing  lever 
is  connected  for  shifting  the  collar  along  the  tubes. 

Couplings  of  this  nature  are  used  for  obtaining  excessive  ad- 
vance of  ignition,  as  on  racing  automobiles. 

187.1.  Eisemann  High-tension  Magneto  with  Automatic 
Spark-advance  Mechanism.  —  The  magneto  has  a  double-wound 
armature  of  the  shuttle  type  which  rotates  between  pole-pieces 
in  the  usual  manner,  and  a  high-tension  distributer  for  directing 
the  secondary  current  to  the  spark-plugs  in  consecutive  order  as 
desired. 

The  device  for  advancing  the  ignition  as  the  speed  of  rotation 
of  the  armature  increases  is  shown  in  the  right-hand  portion  of 
Fig.  238,  which  is  a  longitudinal  section  of  the  magneto.  The 
armature  is  driven  through  a  coupling  which  has  a  groove  or 
grooves  and  a  sleeve  which,  when  moved  longitudinally,  causes 
the  armature  to  rotate  through  part  of  a  revolution  relative  to 
the  driving  shaft,  which  receives  power  from  some  external 
source.  The  method  of  obtaining  automatic  advance  is  to 
connect  the  weights  of  a  centrifugal  shaft-governor  to  the  sleeve 


306 


ELECTRIC  IGNITION 


of  the  coupling  so  that  when  the  weights  are  thrown  outward 
from  the  shaft  by  the  centrifugal  action  due  to  the  rotation  of 


the  armature,  the  movement  of  the  weights  slides  the  sleeve 
along  the  shaft  so  as  to  advance  ignition.     The  safety  spark- 


INTERRUPTER   MAGNETOS   AND   JUMP-SPARK  IGNITION     507 

gap  A  is  shown  distinctly  in  the  illustration.  The  cylindrical 
metal  which  forms  part  of  the  inclosing  wall  of  the  space  in 
which  the  safety-gap  is  inclosed  is  perforated  with  round  holes 
as  shown.  These  hotes  should  be  covered  with  wire  gauze  to 
prevent  ignition  of  an  inflammable  mixture  which  may  collect 
about  the  safety-gap,  or  with  some  such  material  as  mica,  for 
the  same  purpose  and  to  exclude  dust. 

188.   A  magneto  with  a  separately-wound  induction  coil  that 
is  embodied  in  the  magneto  is  shown  in  Fig.  239.     The  end 


FIG.  239.     (See  also  Figs.  240,  241,  and  242.) 
High-tension  Magneto  with  Separately-wound  Transformer. 

cover  and  several  of  the  other  parts  are  removed,  including  the 
interrupter  lever  and  the  distributer  rotor.  Fig.  240  is  a  sec- 
tional view  of  the  magneto,  and  Fig.  241  shows  most  of  the 
parts  separately.  The  wiring  diagram  is  given  in  Fig.  242. 
This  magneto  operates  on  the  interrupted  short-circuit  system 
that  is  shown  in  Fig.  223. 

The  armature  is  of  the  shuttle  type  with  one  winding.  The 
condenser  18  is  just  above  the  armature,  and  a  non-trembler 
transformer  spark-coil  10  is  located  between  the  condenser  and 
the  crown  n  of  the  magnets.  The  interrupter-lever  is  operated 
by  a  pair  of  rolls  in  the  ends  of  the  roll-carrier  25,  which  is  rigidly 
fastened  to  the  armature  shaft.  The  beginning  of  the  armature 
winding  is  grounded  on  the  armature  core.  The  end  of  the 


308 


ELECTRIC  IGNITION 


FIG.  240. 
Longitudinal  Section  of  Fig.  239. 

1.  Armature. 

2.  Insulated  fastening  screw  connected  to  armature  winding. 

3.  Primary  bridge  for  carrying  4. 

4.  Contact-carbon  pressed  against  2. 
6.  Hard  rubber  block. 

8.   Stirrup  spring  for  holding  interrupter  lever  in  place. 

10.  Transformer. 

11.  Magnets,  crown  of. 

13.  High-tension  terminal  of  transformer. 

14.  Blade-spring  connector  between  13  and  15. 

15.  Distributer  rotor. 

1 6.  Carbon  brush  in  distributer  rotor. 

17.  Terminals  for  wire  cables. 

18.  Condenser. 

20.  Coupling  for  driving  the  armature. 

21.  Fastening  nut  for  coupling. 
23.  Cover. 

25.  Roll-carrier  of  interrupter. 


INTERRUPTER  MAGNETOS  AND  JUMP-SPARK  IGNITION     309 

armature  winding  is  connected  to  the  insulated  stationary  con- 
tact of  the  interrupter,  also  to  the  primary  of  the  spark-coil  and 
one  side  of  the  condenser,  so  that  the  armature,  interrupter, 
spark-coil,  and  condenser  are  all  four  in  parallel  with  each  other. 
The  high-tension  current  from  the  spark-coil  is  carried  to  the 
distributer  rotor  which  directs  it  to  the  different  spark-plugs  in 
the  usual  manner.  A  terminal  is  provided  which  connects  to 
ground  through  a  hand-switch.  When  the  latter  is  closed,  the 
armature  circuit  is  permanently  closed  so  as  to  cut  out  ignition. 


FIG.  241. 
Parts  of  Fig.  239. 

The  armature  is  driven  by  means  of  a  coupling  which  rotates 
the  armature  through  part  of  a  revolution  relative  to  the  shaft 
which  drives  it,  when  the  spark-control  is  operated  to  advance 
or  retard  the  ignition.  The  interrupter  is  permanently  fixed  in 
position  relative  to  the  magnet-poles.  The  magneto,  therefore, 
gives  a  spark  of  uniform  strength  at  a  given  speed,  whatever  the 
setting  of  the  ignition  relative  to  advance  and  retard. 

189.  Movable  Extension  of  Magnet-Poles  for  Constant 
Strength  of  Spark.  —  This  method  of  securing  a  nearly  constant 
strength  of  the  ignition  spark  for  positions  of  advance  and  retard 


ELECTRIC  IGNITION 

of  the  ignition,  at  any  given  speed,  has  been  applied  to  shuttle- 
wound  magnetos.  The  more  usual  method  of  applying  it  is  to 
make  the  bore  of  the  magnet-poles  considerably  larger  than  the 
diameter  of  the  armature,  and  insert  a  movable  piece  of  magnetic 
material  between  each  of  the  stationary  poles  and  the  armature. 
Ordinarily  a  longitudinal  portion  of  a  soft  steel  or  iron  tube  is 


Primary  Circuit 

Secondary  Circuit 

Ground  Circuit  through.Frame 

FIG.  242. 
Connections  of  Fig.  239. 

placed  between  each  of  the  poles  and  the  armature.  The  device 
in  one  of  its  forms  resembles,  in  a  measure,  the  rotating  shield 
shown  in  Fig.  28  without  the  extension  for  a  brush  at  one  end. 

Fig.  243  is  a  sectional  view  of  the  stationary  magnet-poles, 
movable  extensions  of  the  poles,  and  the  core  of  a  shuttle-wound 
armature.  The  interrupter  of  the  magneto  and  the  movable 
extensions  of  the  poles  are  fastened  together  so  that  they  move 
as  one  piece  when  the  interrupter  is  rocked  to  advance  or  retard 
the  spark.  The  interrupter  is  set  to  break  the  circuit  while  the 


INTERRUPTER  MAGNETOS  AND  JUMP-SPARK  IGNITION     311 


armature  is  passing  through  the  position,  relative  to  the  movable 
extensions  of  the  poles,  that  is  shown  in  the  figure.  In  this 
position,  the  edges  of  the  crowned  surfaces  of  the  armature  core 
have  passed  a  short  distance  beyond  a  position  opposite  the 
movable  extensions  i  and  2  of  the  poles.  This  short  distance  is 


(A)  (B) 

FIG.  243. 
Movable  Magnetic  Shield  between  Pole-pieces  and  Rotary  Armature. 

about  the  same  in  amount  in  both  (A)  and  (B),  in  which  (A) 
represents  the  position  of  the  pole  extensions  for  advanced  igni- 
tion, and  (B)  their  position  for  retarded  ignition. 

The  rocking  of  the  pole  extensions  together  with  the  inter- 
rupter has  the  effect,  in  a  way,  of  carrying  the  magnetic  field 
around  with  the  interrupter  when  it  is  rocked.  The  armature  is 
thus,  in  effect,  in  essentially  the  same  position  relative  to  the 
magnetic  field  when  the  interrupter  breaks  the  circuit,  whether 
the  ignition  is  set  early  or  late.  The  ignition  spark  is,  therefore, 
of  about  the  same  strength  for  all  positions  of  the  interrupter 
from  that  for  earliest  ignition  to  that  for  latest  ignition. 

190.  Pittsfield  Magneto  with  Stationary  Armature  and  Rock- 
ing Pole-Extensions.  —  Fig.  244  is  an  exterior  view  of  the  mag- 
neto. Fig.  245  is  a  longitudinal  section.  Fig.  246  shows  the 
interrupter,  and  Fig.  247  is  a  cross-section  on  A-B  of  Fig.  245. 

The  construction  of  this  magneto  is  unusual,  in  that  the  sta- 
tionary coils  6  of  the  armature  are  not  between  the  pole -pieces 
of  the  permanent  magnets,  but  are  wound  around  a  soft  iron  or 
steel  core  5  which  is  connected  to  two  laminated  soft  iron  or 
steel  bars  4  that  extend  in  between  the  poles  of  the  permanent 
magnets  3.  The  laminated  bars  4  are  held  rigidly  in  place  by 


312  ELECTRIC  IGNITION 

non-magnetic  parts  2  and  the  non-magnetic  base  of  the  magneto. 
These  and  the  pole -pieces  of  the  permanent  magnets  are  bored 
cylindrical  to  fit  a  longitudinally  slotted  iron  sleeve  which  has 
four  slots  so  as  to  leave  four  bars  28.  The  inductor  i  rotates 
inside  of  the  slotted  sleeve.  The  inductor  has  the  form  of  a 
thick  tube  slotted  through  from  side  to  side,  the  width  of  the 


FIG.  244.     (See  also  Figs.  245,  246,  and  247.) 

High-tension  Magneto  with  Stationary  Double- wound  Armature,  Rotary  Inductor, 
and  a  Rocking  Magnetic  Shield  between  the  Pole-pieces  and  the  Inductor. 
Pittsfield  Spark  Coil  Company,  Dalton,  Massachusetts. 

slot  being  somewhat  less  than  the  inside  diameter  of  the  tube. 
The  metal  of  the  inductor  is  shown  shaded  in  Fig.  247. 

As  the  inductor  revolves,  it  alternately  directs  the  magnetic 
flux  from  the  permanent  magnets  through  the  bars  4  and  core 
of  the  armature  windings  and  cuts  off  the  flux  through  the  arma- 
ture core.  While  the  inductor  is  in  the  position  shown,  the 
magnetism  flows  from  the  north  pole -piece  of  the  permanent 
magnets  directly  through  the  two  sides  of  the  inductor  to  the 
south  pole -piece  of  the  permanent  magnets.  When  the  inductor 
has  rotated  one -eighth  of  a  revolution  from  the  position  shown, 
the  magnetic  flux  is  then  from  the  north  pole -pieces  of  the  per- 
manent magnets  through  the  upper  side  of  the  inductor  to  the 


INTERRUPTER  MAGNETOS   AND  JUMP-SPARK  IGNITION     313 

upper  bar  4,  then  through  the  upper  bar  to  the  armature  core  5, 
down  through  the  armature  core  to  the  lower  bar  4,  and  through 
this  bar  to  the  lower  side  of  the  inductor,  and  on  through  this 
side  of  the  inductor  to  the  south  pole -piece  of  the  permanent 
magnets.  The  magnetic  flux  is  of  course  through  the  slotted 
tube,  or  magnetic  shield,  28,  when  going  from  the  inductor  to  or 
from  the  pole -pieces  and  bars  4.  When  the  indicator  has  rotated 


27- 


19'       A      1        28      21    2 


FIG.  245. 
Longitudinal  Section  of  Fig.  244. 

a  quarter-revolution  from  the  position  shown,  there  is  no  mag- 
netic flux  through  the  armature  core.  At  three-eighths  of  a 
revolution  (from  the  position  shown)  the  magnetic  flux  through 
the  armature  core  is  again  at  or  near  its  maximum  value,  but  in 
the  opposite  direction  from  that  at  one-eighth  of  a  revolution. 
At  half  a  revolution  there  is  no  flux  through  the  armature  core. 
The  same  conditions  exist  again  during  the  remaining  half- 
revolution.  There  are,  therefore,  four  electric  impulses  induced 
in  the  armature  coils  during  each  revolution  of  the  inductor. 


ELECTRIC  IGNITION 


The  beginning  of  the  primary  winding  of  the  armature  is  con- 
nected to  the  frame  of  the  magneto  by  the  screw  7.  The  end  of 
the  primary  winding  is  connected  to  the  beginning  of  the  second- 
ary winding,  and  the  junction  of  the  two  windings  is  connected 
to  the  insulated  plate  8,  which  has  electric  connection  to  the 
insulated  stationary  contact-piece  9  of  the  interrupter.  The 
stationary  (insulated)  contact-screw  10  of  the  interrupter  is 


FIG.  246. 

Interrupter  End  of  Fig.  244  with  some 
of  the  Parts  Removed. 


FIG.  247. 

Cross-section  of  Fig.  244  on  Plane  A 
of  Fig.  245. 


-B 


carried  by  9.  The  movable  contact-screw  13  is  in  the  end  of  the 
interrupter-lever  12.  The  flat  spring  14  acts  on  lever  12  to  press 
the  contact -points  together.  The  interrupter-lever  is  operated 
by  a  four-lobed  cam  15  that  is  fastened  to  the  inductor  shaft 
and  rotates  with  the  inductor.  The  interrupter-lever  is  elec- 
trically connected  to  the  frame  of  the  magneto,  so  that  when 
the  contact-points  of  the  interrupter  are  pressed  together  the 
primary  circuit  is  closed.  The  cam  forces  the  contacts  apart 
four  times  each  revolution  of  the  inductor,  thus  interrupting  the 


INTERRUPTER  MAGNETOS   AND  JUMP-SPARK  IGNITION     315 

primary  current  at  each  insjant  that  it  reaches  its  maximum 
value. 

The  interrupter  is  rigidly  connected  to  the  slotted  tube,  or 
shield,  28,  and  both  are  rocked  together  by  means  of  the  timing 
lever  35  to  vary  the  instant  of  ignition.'  Rocking  the  tubular 
shield  has  the  effect  of  moving  the  magnet-poles  so  as  to  always 
have  the  current  at  or  near  its  maximum  value  at  the  instant  of 
its  interruption,  as  has  been  explained  in  the  preceding  section. 

The  high-tension  terminal  of  the  secondary  winding  of  the 
armature  is  connected  to  the  contact-piece  18,  against  which  the 
insulated  carbon  brush  20  is  pressed  by  a  spring.  The  high- 
tension  current  flows  from  the  brush  20  through  the  conductor 
21  to  the  metal  rotor  23  of  the  distributer.  Conductor  21  is 
covered  with  insulation  19,  and  the  metal  rotor  of  the  distributer 
is  carried  by  the  insulation  22.  The  stationary  contact-pieces 
25  of  the  distributer  are  connected  by  conductors  26  to  the 
terminal  block  27,  from  which  wires  lead  to  the  spark-plugs. 

Condenser  16  has  one  side  connected  to  the  junction  of  the 
primary  and  secondary  windings,  and  the  other  side  grounded 
to  the  body  of  the  magneto.  Terminal  29  is  also  connected  to 
the  junction  of  the  primary  and  secondary  windings.  When 
this  terminal  is  connected  to  ground,  ignition  is  cut  off  on  account 
of  the  primary  circuit  being  thus  permanently  closed  through 
a  low-resistance  path  in  parallel  with  the  interrupter. 

The  rotative  speed  of  the  inductor,  for  a  four-cycle  motor  with 
four  combustion  chambers,  must  be  half  that  of  the  crank-shaft, 
which  is  the  same  as  that  of  the  cam-shaft,  since  there  are  four 
sparks  produced  during  each  revolution  of  the  inductor. 

A  modified  form  of  this  magneto  interrupts  the  current  only 
twice  during  each  revolution  of  the  inductor,  and  therefore  pro- 
duces only  two  sparks  per  revolution  of  the  magneto  inductor. 
This  modified  form  must  rotate  twice  as  fast  as  the  one  just 
described. 

Of  the  numbered  parts  not  mentioned,  17  is  the  condenser 
case,  24  the  front  plate  of  the  magneto,  30  the  rear  housing,  31 
the  latch  for  holding  the  rear  housing  in  place,  and  32,  33,  and 
34  are  screws  for  holding  the  removable  parts  in  place. 


ELECTRIC  IGNITION 

191.   Mea  Magneto  with  Rocking  Magnets.  —  This  magneto 
has  several  distinctive  features  that  are  not  found  in  those  of 


FIG.  248.     (See  also  Figs.  249,  250,  251,  252,  253,  254,  and  Plates  VI  and  VII.) 

Mea  High-tension  Magneto  Mounted  on  Trunnions.     Marburg  Bros.,  Broadway 
&  58th  Street,  New  York  City. 


FIG.  249. 
Bell-shaped  Field-Magnets  of  Mea  Magneto,  Fig.  248. 

earlier  design.  The  principal  unique  feature  is  the  use  of  parts 
of  such  a  form  that  they  can  be  assembled  compactly  so  that  the 
entire  magneto  can  be  rocked  on  a  supporting  frame,  or  base, 


INTERRUPTER  MAGNETOS  AND  JUMP-SPARK  IGNITION     317 

for  advancing  and  retarding  the  ignition.  The  advance  and 
retard  can  be  carried  to  any  extent  ever  required  without 
affecting  the  strength  of  the  ignition  spark.  The  magnets  and 
interrupter  are  of  distinctive  form,  and  there  is  a  window 
through  which  the  position  of  the  distributer  rotor  can  be 
observed. 

Fig.  248  is  a  full  view  of  the  entire  magneto  resting  on  its 
supporting  frame.  The  magnets  are  shown  in  Fig.  249  with  the 
pole -pieces  fastened  to  them.  Fig.  250  is  a  longitudinal  section 
of  the  magneto,  and  Fig.  251  is  a  full  view  of  the  interrupter  end 
with  the  cover  of  the  interrupter  removed.  Fig.  252  shows  the 
working  parts  of  the  interrupter. 

The  magnets  are  called  "  bell-shaped  "  by  the  manufacturer. 
The  armature  is  of  the  shuttle  type  with  double  winding.  The 
armature  shaft  lies  parallel  with  the  length  of  the  magnets,  and 
one  end  of  the  shaft  passes  through  a  hole  in  the  crown  of  the 
magnets.  The  armature  does  not  differ  essentially  from  those 
of  the  shuttle  type  ordinarily  used. 

The  parts  of  the  magneto  are  shown  in  detail  in  Plates  VI 
and  VII. 

The  wiring  diagram  is  essentially  the  same  as  in  Fig.  224. 
The  beginning  of  the  low-tension  winding  is  grounded  on  the 
armature  core.  The  end  of  the  low- tension  winding  is  connected 
to  the  beginning  of  the  secondary  winding  of  the  armature,  and 
the  high-tension  end  of  the  secondary  winding  is  connected  to  the 
insulated  slip-ring,  or  collector-ring  4,  against  which  the  insulated 
carbon  brush  77  bears.  Current  from  the  high-tension  end  of  the 
winding  passes  through  the  brush  7  7,  metal  bridge  84,  and  brush  69 
to  the  two  brushes  68  of  the  distributer  rotor.  Each  of  these  two 
distributer  brushes  distributes  current  to  its  own  two  of  the 
four  contact-pieces  to  which  the  terminals  of  the  spark-plug  wires 
are  connected.  The  use  of  two  brushes  in  the  distributer  rotor, 
as  stated,  makes  it  possible  to  have  a  rotor  of  small  diameter 
without  bringing  the  stationary  contact-pieces  of  the  distributer 
unduly  close  together. 

The  junction  of  the  primary  and  secondary  windings  is  con- 
nected to  the  insulated  plate  of  the  condenser  12.  This  plate 


318  ELECTRIC  IGNITION 


FIGS.  250,  251  and  252. 
i.  Armature. 

4.   Collector-ring,  or  slip-ring. 
7.  Pinion  gear  for  driving  the  distributer  rotor. 
12.   Condenser. 
17,  1 8.   Ball  bearings. 

24.   Fastening  and  conducting  screw. 

27.  Interrupter  disk. 

28.  Insulated  plate  of  interrupter. 

30.  Interrupter  spring. 

31.  Fiber  roller  of  interrupter. 

33.  Contact-point  of  interrupter. 

34.  Contact-point. 

40.   Cam-disk  of  interrupter. 

46.  Carbon  brush. 

47.  Brush-holder. 
50.   Ground  terminal. 
53.   Base  of  magneto. 
66.   Distributer  rotor. 

68.  Brushes  of  distributer  rotor. 

69.  Carbon  brush  bearing  against  distributer  rotor. 

70.  Stationary  plate  of  distributer,  with  contact-pieces. 
72.   Gear  on  distributer  rotor. 

74.   Cover  of  interrupter  housing. 

76.  Brush-holder. 

77.  Carbon  brush  on  collector  ring. 

78.  Brush  making  ground  connection  for  armature. 

84.   Connecting  bridge  between  77  and  the  distributer  rotor. 

88.   Arm  for  controlling  the  time  of  ignition. 

91.   Metal  plate  for  supporting  the  brushes  77  and  78. 
100.   Magnets. 
108.   High-tension  terminals. 


INTERRUPTER  MAGNETOS  AND  JUMP-SPARK  IGNITION    319 


66   70 


69  78    89   84   76    91    77 


5S  1  12  4: 

FIG.  250. 
Longitudinal  Section  of  Fig.  248. 


18    100     X24 


FIG.  251. 

Interrupter  End  of  Fig.  248  with  In- 
terrupter Cover  removed. 


27, 


FIG.  252. 
Interrupter  of  Fig.  248. 


320  ELECTRIC  IGNITION 

is  threaded  to  receive  the  fastening  screw  24  that  holds  the  inter- 
rupter in  place  and  conducts  the  primary  current  to  its  insulated 
block  28. 

The  interrupter  spring  30,  which  carries  the  movable  contact- 
point,  is  fastened  to  the  insulated  block  28.  The  interrupter 
spring  has  the  general  form  of  a  thin  washer  that  has  been 
cut  through  on  one  side.  The  block  28  is  fastened  to  the  disk 
27  but  is  insulated  from  it.  The  stationary  contact-point  of 
the  interrupter  is  mounted  on  the  disk  27,  and  both  are  elec- 
trically connected  (grounded)  to  the  frame  of  the  magneto. 
The  interrupter  spring  is  forced  back,  in  a  direction  approx- 
imately parallel  to  the  length  of  the  armature  shaft,  by  the  fiber 
roller  31  at  the  instant  the  primary  circuit  is  to  be  broken. 
The  roller  is  carried  in  a  pocket  in  the  disk  27.  As  the  disk  27 
and  interrupter  spring  rotate  with  the  armature,  the  roller  strikes 
successively  against  two  projecting  lobes  on  the  stationary 
cam-disk  40,  and  the  roller  is  thus  forced  against  the  inter- 
rupter spring  so  as  to  push  the  latter  back  and  separate  the 
contact-points.  The  two  lobes  are  half  a  revolution  apart,  so 
that  the  circuit  is  broken  twice  during  each  revolution.  The 
parts  of  the  interrupter  are  shown  in  Plate  VI,  Nos.  26  to  42 
inclusive. 

The  numbers  i,  2,  3,  4  are  marked  on  the  gear-wheel  which  is 
attached  to  the  distributer  rotor  of  a  magneto  for  four  combus- 
tion chambers.  This  numbering  is  shown  in  Fig.  253.  When 
the  armature  is  in  the  position  at  which  the  interrupter  contacts 
should  just  begin  to  separate,  one  of  these  numbers  should  register 
with  a  circular  window  in  the  upper  part  of  the  distributer  casing. 
In  Fig.  253  the  numeral  i  registers  with  the  window,  and  the 
armature  is  in  the  position,  during  its  clockwise  rotation,  at 
which  the  interrupter  contacts  should  begin  to  separate.  When 
the  armature  has  made  half  a  revolution  from  this  position,  the 
numeral  2  will  register  with  the  window.  The  numbers  can  be 
seen,  in  the  actual  magneto,  only  when  they  register  with  the 
window.  In  the  illustration,  the  lower  part  of  the  casing  is 
broken  away  to  show  the  numbers  not  at  the  window.  The 
distance  between  the  edge  of  the  armature  core  and  the  edge  of 


INTERRUPTER  MAGNETOS   AND  JUMP-SPARK  IGNITION     321 


the  magnet-pole  is  given  as  1.5  millimeters  (about  yy  or  .06 
of  an  inch)  in  the  figure.  In  Fig.  254  the  corresponding  positions 
of  the  armature  and  distributer  are  shown  for  counter-clockwise 
rotation  of  the  armature. 


FlGS.  253  and  254. 

Relative  Rotative  Positions  of  Armature  and  Distributer  in  Fig.  248  for  Right- 
hand  and  Left-hand  Rotation. 

There  is  a  safety  spark-gap  for  protecting  the  insulation  of 
the  magneto  against  excessive  electric  pressure  in  case  one  of  the 
wires  becomes  disconnected  from  its  spark-plug.  The  safety- 
gap  cannot  be  seen  in  the  illustration,  however. 


322  ELECTRIC  IGNITION 


PLATE  VI. 

1.  Complete  armature  with  condenser,  small  gear-wheel,  slip-ring,  and  two  ball- 

bearings without  outer  race  collar. 

2.  Front  armature-disk  with  spindle  without  other  parts. 

3.  Rear  armature-disk  with  spindle  without  other  parts. 

4.  Slip-ring. 

5.  Front  ball-bearing  without  race  collar. 

6.  Rear  ball-bearing  without  race  collar. 

7.  Small  gear-wheel. 

8.  Washer  for  slip-ring. 

9.  Fastening  ring  for  8. 

10.  Washer  for  spindle  cone. 

11.  Nut  for  10. 

12.  Complete  condenser  with  brass  furniture. 

13.  Silk  strip  for  the  circumference  of  the  condenser. 

14.  Fastening  screw  of  the  condenser. 

15.  Silk  insulating  strip  for  the  condenser. 

16.  Mica  insulating  plate  for  the  condenser. 

17.  Complete  front  ball-bearing. 

1 8.  Complete  rear  ball-bearing. 

19.  Fastening  screw  for  the  small  gear-wheel. 

20.  Fastening  screw  for  the  front  armature-disk. 

21.  Fastening  screw  for  the  rear  armature-disk. 

22.  Felt  disk  for  the  front  ball-bearing. 

23.  Felt  disk  for  the  rear  ball-bearing. 

24.  Fastening  screw  for  contact-breaker. 

25.  Insulating  piece  for  24. 

26.  Complete  contact-breaker. 

27.  Contact-breaker  disk. 

28.  Contact-piece  for  contact-breaker  spring. 

29.  Insulation  for  contact-piece. 

30.  Contact-breaker  spring. 

31.  Contact-breaker  roller. 

32.  Safety  screw  for  31. 

33.  Short  platinum  screw  for  contact-breaker. 

34.  Long  platinum  screw  for  contact-breaker. 

35.  Fastening  screw  for  contact-piece  28. 

36.  Vulcanite  insulation  for  35. 

37.  Fastening  screw  for  contact-breaker  spring. 

38.  Washer  for  37. 

39.  Insulation  bush  for  contact-breaker  disk. 

40.  Stud  ring. 

41.  Fastening  screw  for  stud  ring. 

42.  Safety  pin  for  stud  ring. 

43.  Case  for  rear  ball-bearing  complete  with  race  collar  and  fastening  screw. 

44.  Race  collar  of  rear  ball-bearing. 

45.  Fastening  screw  for  ball-bearing  case. 

46.  Carbon  brush  for  cover  of  contact-breaker  case. 

47.  Complete  fastening  for  46  with  nut. 

48.  Body  for  47. 

49.  Fastening  screw  for  48. 

50.  Nut  for  switch  wire  (short  circuit). 

51.  Mica  disks  for  48. 


INTERRUPTER  MAGNETOS  AND  JUMP-SPARK  IGNITION      323 


2  1 


13 


18 


19  20  21 


23  23 

i  k 


26  ( 


- 


25 

O 


24 


35  37 

38     .33 

39  36 

O  O 


31 


27 


29  |f9|  ZB  ^  (    3( 

itCQ  ''* 


i  32 


46 


^1  **f 

L_O       I      Ci 


PLATE  VI. 
Parts  of  Fig.  248. 


324  ELECTRIC  IGNITION 


PLATE  VII. 

52.  High-tension  cable  with  terminal  and  cable  sleeve. 

53.  Complete  base  for  magneto. 

54.  Hinged  link  for  closure  of  the  base  bearing. 

55.  Tension  screw  for  54. 

56.  Joint  nut  for  55. 

57.  Counter  nut  for  56. 

58.  Cover  of  the  rear  base  bearing. 

59.  Cover  of  the  front  base  bearing. 

60.  Oil  cover  for  58  or  59. 

61.  Side  bearing  cover. 

62.  Mica  cover  for  inspection  opening. 

63.  Ring  around  opening. 

64.  Fastening  screw  for  63. 

65.  Fastening  screw  of  side  bearing-cover. 

66.  Distributer  finger. 

67.  Fastening  screw  for  distributer  finger. 

68.  Radial  distributer  carbon  with  spring. 

69.  Axial  distributer  carbon  with  spring. 

70.  Distributer  case. 

71.  Fastening  screw  with  nut  for  distributer  case. 

72.  Large  gear-wheel. 

73.  Case  for  contact-breaker. 

74.  Cover  for  73. 

75.  Screw  for  74. 

76.  Carbon  holder. 

77.  Carbon  with  spring  for  76. 

78.  Carbon  with  spring  for  body  contact-screw. 

79.  Shaft  of  the  distributer  complete. 

80.  Spindle  for  distributer  gear-wheel. 

8 1.  Fastening  screw  for  80. 

82.  Disk  with  safety  pin. 

83.  Fastening  screw  for  82. 

84.  Connection  piece  between  carbon  holder  and  distributer. 

85.  Magneto  casing  complete  without  cover. 

86.  Spring  of  the  closure. 

87.  Fastening  screw  for  86. 

88.  Timing  lever. 

89.  Cover  for  magneto  casing  complete. 

90.  Spring  for  oil-hole. 

91.  Fastening  screw  for  90. 

92.  Catch-bolt  with  nut  for  cover  of  the  magneto  casing. 


INTERRUPTER  MAGNETOS   AND   JUMP-SPARK   IGNITION        325 


87    86        88 


PLATE  VII. 
Parts  of  Fig.  248, 


CHAPTER  XXI. 


HIGH-TENSION  DUAL  AND   COMBINED   IGNITION   SYSTEMS. 

192.  Introductory.  —  Of  the  ignition  diagrams  in  this  chapter 
those  which  give  the  electric  connections  in  detail  are  either  in 
accordance  with  blue  prints  and  drawings  kindly  furnished  by 
the  manufacturers  or  their  agents,  or  are  diagrams  made  by  the 
Author  and  approved  by  the  manufacturers  or  their  agents. 
The  illustrations  showing  the  general  external  appearance  of  the 
ignition  systems  are  generally  taken  from  the  trade  literature 
of  those  who  make  and  sell  ignition  apparatus  or  put  it  into  use. 

Most  of  the  detail  dia- 
grams from  manufacturers 
and  agents  have  been  modi- 
fied slightly  in  unimportant 
details  in  order  to  make 
them  conform  more  nearly 
with  the  conventions  used 
throughout  this  book. 

Some  of  the  systems  repre- 
sented are  early  ones  that 
were  much  used  at  one  time, 
but  have  been  improved 
upon  by  the  manufacturers, 
and  in  some  cases  almost  or 
quite  discarded  by  them  so 
far  as  new  installations  are 
concerned.  It  is  believed, 
however,  that  these  earlier 
systems  deserve  description 
on  account  of  the  importance 
they  once  had  and  because 
many  of  them  are  still  in  use  where  they  were  installed  in  earlier 
constructions. 

326 


Switch 


Fig.  255.     (See  also  Fig.  256.) 
Remy  High-tension  Ignition  System. 


HIGH-TENSION  DUAL  AND  COMBINED  IGNITION  SYSTEMS     327 

193.  Remy  Ignition  System  with  Separate  Transformer.  — 
The  Remy  magneto  has  been  described  in  another  chapter.  The 
general  outside  appearance  of  the  ignition  system  used  with 
this  magneto  is  shown  in  Fig.  255.  A  non- trembler  transformer 
spark-coil  with  its  own  condenser  is  used  in  connection  with  both 
the  magneto  and  a  battery.  A  turn-switch  and  a  push-button 
are  mounted  on  the  box  which  contains  the  transformer  and  the 


FIG.  256.     (See  also  Fig.  255.) 
Internal  and  External  Connections  for  Remy  High-tension  Ignition  System. 

condenser.  The  battery  is  for  starting  the  motor  on  "  spark  " 
by  pushing  and  releasing  the  push-button  when  the  switch  is 
set  in  the  battery  position. 

The  wiring  connections  are  shown  in  detail  in  Fig.  256.  The 
insulated  terminal  8  of  the  stationary  armature  of  the  magneto 
is  connected  to  the  contact-point,  or  pole,  M  (represented  by  a 
dotted  circle),  of  the  switch.  The  other  terminal  of  the  armature 
winding  is  connected  to  the  ground-screw  7  of  the  magneto.  The 
ground-screw  is  connected  by  a  wire  to  one  side  each  of  the 


328  ELECTRIC  IGNITION 

battery,  the  push-button,  and  the  condenser.  The  insulated 
terminal  13  of  the  magneto  interrupter  is  connected  to  the  low- 
tension  terminal  F  of  the  transformer,  which  is  also  connected 
to  one  side  of  the  condenser.  The  insulated  terminal  13  is  also 
connected  to  a  crescent-shaped  piece  of  metal  C-C  in  the  switch. 
C-C  is  not  connected  to  any  of  the  contact-points,  or  poles,  of 
the  switch,  but  is  connected  to  one  of  the  contacts  of  the  push- 
button. One  side  of  the  battery  is  connected  to  the  pole  B  of 
the  switch.  The  junction  K  of  the  two  windings  of  the  trans- 
former is  connected  to  both  of  the  poles  D  and  E  of  the  switch. 
The  high-tension  terminal  S  of  the  transformer  is  connected  to 
the  rotor  14  of  the  distributer.  The  cross-bar  of  the  switch  is 
not  shown  in  its  position  corresponding  to  that  in  which  the 
diamond-shaped  switch -handle  is  represented.  It  is  shown  by 
broken  lines  in  two  positions.  In  one  of  these  positions,  when 
connecting  M  and  D,  the  magneto  is  cut  into  circuit  so  that  its 
current  is  used  and  the  battery  is  out  of  circuit.  In  the  other 
position  of  the  switch-bar,  when  connecting  the  poles  B  and  E, 
the  battery  is  in  circuit  and  the  armature  of  the  magneto  is  cut 
out.  The  interrupter  of  the  magneto  is  always  kept  in  circuit, 
since  it  must  interrupt  the  current  whether  it  comes  from  the 
battery  or  the  armature  of  the  magneto.  The  condenser  is  in 
parallel  with  both  the  interrupter  of  the  magneto  and  the  push- 
button. 

When  the  switch  is  set  to  use  magneto  current,  the  path  of 
the  primary  current,  assuming  a  direction  of  flow,  is  from  the 
insulated  terminal  8  of  the  armature  winding  to  switch-pole  M 
through  the  switch-bar  from  M  to  D,  thence  to  H  and  on  to 
the  junction  terminal  K  of  the  transformer,  through  the  trans- 
former primary  to  F  and  on  to  the  insulated  terminal  13,  which 
carries  it  to  the  contact-points  of  the  interrupter,  from  which  it 
goes  through  the  interrupter  lever  9  to  the  ground-screw  7  to 
which  the  other  end  of  the  armature  winding  is  connected. 
Since  the  primary  current  is  an  alternating  one,  it  of  course 
flows  in  this  direction  at  one  impulse  and  in  the  opposite  direction 
at  the  next  impulse. 

The  secondary  current  flows  from  the  high-tension  terminal  5 


HIGH-TENSION   DUAL   AND   COMBINED   IGNITION  SYSTEMS    329 

of  the  transformer  to  the  rotor  14  of  the  distributer,  and  the 
rotor  directs  it  to  the  spark-plugs.  From  the  spark-plugs  the 
high-tension  current  goes  through  ground  to  the  ground-screw  7, 
then  through  the  armature  winding  to  8  and  on  through  the 
connecting  wire  to  the  switch -pole  M,  through  the  switch -bar 
to  D,  thence  to  H  and  the  junction  terminal  K  of  the  trans- 
former. It  is  probable  that  some  of  the  high-tension  current 
does  not  go  through  the  armature  winding  as  just  stated,  but  goes 
from  the  ground-screw  7  through  the  interrupter,  jumping  the 
space  which  exists  at  the  instant  between  the  contact-points  of 
the  interrupter,  so  as  to  reach  the  insulated  terminal  13,  then 
flows  through  the  connecting  wire  to  F  and  on  through  the 
primary  of  the  transformer  to  the  junction  point  K,  thus  com- 
pleting the  circuit  when  the  secondary  of  the  transformer  is 
included.  The  high-tension  current  of  course  also  alternates 
in  its  direction  of  flow  in  the  same  manner  that  the  primary 
current  does  while  the  system  is  operating  on  magneto  current. 
The  battery  circuit  is  open  at  the  switch  when  the  magneto  is 
cut  into  circuit,  since  under  this  condition  the  pole  B  of  the 
switch  has  no  connection  with  anything  but  one  side  of  the 
battery. 

When  the  switch  is  set  to  the  battery  position,  the  poles  B 
and  E  are  connected,  and  the  magneto  circuit  is  left  open  at  the 
pole  M.  The  path  of  the  battery  current  is  then  from  B,  through 
the  switch -bar  to  E,  thence  to  H  and  on  to  the  junction  terminal 
K  of  the  transformer,  through  the  transformer  primary  to  F  and 
on  through  the  connecting  wire  to  the  insulated  interrupter 
terminal  13,  then  through  the  interrupter  to  the  ground-screw  7 
and  on  through  the  connecting  wire  to  P  and  the  battery.  The 
path  of  the  high-tension  current  is  from  the  secondary  high- 
tension  terminal  5  to  the  distributer,  the  spark-plugs  and  ground 
in  series  as  before  to  the  ground-screw  7,  but  from  7  it  goes 
through  the  connecting  wire  to  P,  thence  through  the  battery 
and  switch  to  B  and  E,  then  to  H  and  the  junction  terminal  K 
of  the  transformer.  Just  as  in  the  case  of  using  magneto  cur- 
rent, part  of  the  secondary  current  may  go  from  7  through  the 
interrupter  to  the  primary  terminal  of  the  transformer. 


330 


ELECTRIC  IGNITION 


If  the  push-button  contacts  are  pressed  together  while  the 
switch  is  set  in  battery  position  and  the  contacts  of  the  magneto 
interrupter  are  separated,  then  current  will  flow  from  the  battery 
to  the  switch-pole  B,  switch-bar  to  E,  then  to  H  and  on  to  the 
junction  terminal  K,  through  the  primary  winding  of  the  trans- 
former to  Fj  thence  to  G  and  on  to  the  crescent-shaped  bar 
C-C,  to  and  through  the  push-button  and  on  to  P  and  the 
battery.  If  the  push-button  contacts  are  then  allowed  to  spring 
apart  quickly,  the  interruption  of  the  batteiy  current  will  cause 
a  spark  to  jump  at  one  of  the  spark-plugs.  In  this  manner  a 

motor  can  be  started  on  spark 
when  there  is  a  combustible 
charge  in  the  combustion  cham- 
ber at  whose  spark-plug  the 
spark  jumps.  The  condenser, 
being  in  parallel  with  the  push- 
button, aids  in  the  production  of 
a  jump-spark  in  the  same  manner 
that  it  aids  the  interrupter  when 
the  latter  is  operating. 

The  push-button  can  also  be 
used  to  cut  out  ignition  when 
the  motor  is  running  on  either 
battery  current  or  magneto  cur- 
rent. This  is  done  by  keeping 
the  contacts  of  the  push-button 
pressed  together.  As  long  as  the  contacts  of  the  push-button 
are  kept  pressed  together  there  is  a  permanently  closed  circuit, 
through  which  either  the  battery  current  or  the  magneto  current, 
according  to  the  setting  of  the  switch,  can  flow  without  going 
through  the  interrupter.  The  latter  cannot,  therefore,  interrupt 
the  current  so  as  to  produce  an  ignition  spark  as  long  as  the 
push-button  circuit  is  kept  closed. 

194.   Splitdorf  Ignition  System  with  Separate  Transformer.  — 
The  magneto  used  in  this  system  is  shown  in  Fig.  257.     It  has  a 
rotary  armature  of  the  shuttle  type  with  one  winding,  and  is 
provided  with  a  mechanically  operated  interrupter  and  a  high- 


FIG.  257. 

Single-wound  Magneto  with  High- 
tension  Distributer.  C.  F.  Split- 
dorf, New  York  City. 


HIGH-TENSION   DUAL  AND   COMBINED  IGNITION  SYSTEMS      331 


tension  distributer.  The  interrupter  and  distributer  end  of  an 
earlier  type  of  the  magneto  is  shown  in  Fig.  258.  This  earlier  type 
is  shown  because  it  conforms  to  the  wiring  diagram  of  Fig.  259, 
which  gives  the  external  appearance  of  the  connections.  This 
wiring  diagram  is  essentially  the  same  as  that  for  the  later  form 
of  the  magneto. 


10 


5      4.     6 

FIG.  258. 
Interrupter  End  of  Early  Form  of  Splitdorf  Magneto.     Cover  Removed. 

Insulated  outside  terminal  of  armature  winding.    Connected  to  brushes  5,5. 

Insulated  terminal  connected  to  contact-screw  10. 

Ground  terminal  for  connecting  to  outside  wires. 

Insulated  central  rod  or  screw  connected  to  insulated  end  of  armature  coil. 

Brushes  pressing  against  4. 

Insulated  brush-holder  for  5,  5.     Connected  to  A. 

Interrupter  arm,  or  lever.     Grounded. 

Cam  for  lifting  interrupter  arm.     Grounded. 

Tension  spring  for  holding  interrupter  arm  against  cam  and  contact-screw. 

Contact-screw.     Insulated  and  stationary. 

Bracket  for  holding  contact-screw. 

Insulation. 

Distributer  rotor.     High-tension. 

Contact-points  of  terminals  for  wires  leading  to  spark-plugs. 


The  electrical  connections  are  shown  in  detail  in  Fig.  260. 
The  magneto  operates  on  the  interrupted  short-circuit  prin- 
ciple while  using  its  own  current.     An  elementary  system  of  this 


A. 

2. 

3- 

4- 

5.  5- 
6. 

7- 


332 


ELECTRIC  IGNITION 


nature  has  been  shown  in  Fig.  223.  When  the  battery  is  in  use, 
the  interrupter  of  the  magneto  breaks  the  battery  circuit  com- 
pletely at  the  instant  of  ignition. 

In  the  magneto,  one  end  of  the  armature  winding  is  grounded 
to  the  armature  core  and  consequently  to  the  frame  of  the 
machine.  A  ground  terminal  3  is  provided  for  making  connection 
to  an  external  wire.  The  insulated  end  of  the  armature  winding 
is  connected  to  an  insulated  rod,  or  long  screw,  4,  which  passes 
through  the  hollow  spindle  of  the  armature  and  projects  beyond 
the  end  of  the  spindle.  Two  insulated  brushes,  5,  5,  (which 


FIG.  259.     (See  also  Fig.  260.) 
Splitdorf  High-tension  Ignition  System. 


are  replaced  by  a  single  brush  that  bears  against  the  end  of 
screw  4  in  the  more  recent  design)  press  against  the  cylindrical 
surface  of  4  near  its  outer  end.  These  brushes  are  carried  in 
the  brush-holder  6  which  is  electrically  connected  to  the  terminal 
A.  The  stationary  contact-screw  10  is  carried  by  the  insulated 
bracket  n  which  has  the  terminal  2.  The  interrupter-lever  7 
is  pivoted  at  its  right-hand  end  and  held  against  the  cam  8  by 
the  tension  spring  9.  The  cam  is  mounted  on  the  tubular  portion 
of  the  armature  shaft.  The  interrupter-lever  is  grounded  to 
the  frame  of  the  magneto. 


HIGH-TENSION  DUAL  AND  COMBINED  IGNITION  SYSTEMS     333 

When  the  switch-blade  is  set  in  the  magneto  position,  as  in 
Fig.  260,  the  battery  is  cut  out  of  circuit.  The  primary  current 
flows  from  the  insulated  terminal  A  of  the  magneto  to  the  point 
B  of  the  switch.  When  the  contact-points  of  the  interrupter 
7-10  are  separated,  as  shown,  all  of  the  armature  current  flows 
from  B  on  through  the  switch-blade  to  its  pivot  E  and  then 
through  the  permanent  connection  from  E  to  F.  From  F  the 
current  flows  to  and  through  the  primary  winding  of  the  trans- 
former spark-coil,  then  from  the  junction  of  the  two  windings  of 


FIG.  260.     (See  also  Fig.  259.) 
Internal  and  External  Connections  for  Splitdorf  High-tension  Ignition  System. - 

the  latter  back  to  the  ground  terminal  3  of  the  magneto,  which 
brings  it  to  the  armature  winding  again.  But  while  the  contact- 
points  of  the  interrupter  are  together  so  as  to  close  the  circuit 
through  the  interrupter,  the  current  divides  at  the  switch -blade, 
most  of  it  going  to  the  switch-point  C  and  then  by  the  path  2-2 
to  the  insulated  contact-point  10  of  the  interrupter,  and  thence 
through  the  interrupter-lever  to  ground  and  the  grounded  end 
of  the  armature  winding.  The  resistance  of  the  shunt-circuit 
C-2-2-io~7  through  the  closed  interrupter  is  very  much  less  than 
that  of  the  circuit  through  the  spark-coil,  therefore  most  of  the 


334  ELECTRIC  IGNITION 

armature  current  flows  through  the  shunt  circuit  while  the 
interrupter  is  closed.  When  the  interrupter  breaks  the  shunt 
circuit,  at  the  instant  the  armature  current  is  at  or  near  its 
maximum  value,  sufficient  current  is  sent  through  the  spark- 
coil  primary  to  cause  a  spark  to  pass  at  the  spark-plugs. 

The  high-tension  current,  after  flowing  from  the  secondary 
terminal  D  to  the  distributer  and  one  of  the  spark-plugs  in  the 
usual  manner,  can  return  to  the  spark-coil  through  the  per- 
manently closed  circuit  3-3.  Part  of  it  may  go  back  by  way  of 
the  armature  and  part  through  the  interrupter,  however. 

When  the  switch  is  set  in  battery  position,  with  the  finger 
on  the  blade  pointing  to  "  BAT"  the  armature  circuit  of  the 
magneto  is  left  open  at  B.  Battery  current  then  flows  to  the 
switch-point  G,  on  through  the  switch-blade  to  F,  and  thence 
through  the  primary  of  the  spark-coil  and  the  connections  to 
the  ground  terminal  3  of  the  magneto.  This  brings  it  to  the 
grounded  interrupter  lever  7,  from  which  it  flows  through  the  con- 
tact-points of  the  interrupter  to  10,  and  thence  through  the  con- 
nections 2-2-  H  to  the  battery.  The  battery  circuit  is  broken 
by  the  interrupter  at  the  instant  ignition  is  to  occur,  as  has  been 
stated. 

The  push-button  can  be  used  for  starting  the  motor  on  spark 
with  battery  current,  or  for  cutting  out  the  ignition  when  the 
motor  is  running  on  either  battery  current  or  magneto  current. 
Closing  the  push-button  and  then  allowing  its  contacts  to  sepa- 
rate quickly,  when  the  switch  is  in  battery  position  and  the 
interrupter  contacts  open,  produces  an  ignition  spark  at  one  of 
the  plugs.  Keeping  the  push-button  closed  makes  a  permanent 
circuit  in  parallel  with  the  interrupter,  such  that  the  action  of  the 
latter  when  the  motor  is  running  will  not  cause  an  ignition  spark. 

195.  Eisemann  Ignition  System  with  Separate  Transformer.— 
The  external  connections  of  this  system  are  shown  in  Fig.  261, 
and  the  complete  wiring  system  is  shown  conventionally  in 
Fig.  262.  The  magneto  has  an  armature  of  the  shuttle  type 
with  a  single  winding  and  operates  on  the  interrupted  shunt- 
circuit  system.  The  spark-coil  is  of  the  non- trembler  trans- 
former type.  A  battery  is  provided. 


HIGH-TENSION  DUAL  AND  COMBINED  IGNITION  SYSTEMS     335 

The  switch-handle  i  is  shown  in  its  position  for  cutting  off 
ignition,  and  the  switch-plug  which  goes  in  the  hole  2  is  removed. 
In  order  to  throw  in  either  the  battery  or  the  magneto,  the  plug 
must  be  inserted  at  2  and  the  switch-handle  thrown  either  to  the 
left  or  right,  according  to  whether  the  magneto  or  the  battery  is 


FIG.  261.     (See  also  Fig.  262.) 

Eisemann    High-tension    Ignition    System,    Early    Form.     Eisemann-Magneto 
Company,  New  York,  N.  Y.,  and  Detroit,  Michigan. 

to  be  put  into  operation.  The  handle  of  the  switch  is  hinged  at 
the  center  of  the  large  circle.  The  arm  which  extends  from  the 
center  of  the  large  circle  up  to  2  does  not  swing  with  the  handle, 
but  remains  permanently  in  the  position  shown. 

When  the  magneto  is  cut  into  circuit  by  putting  the  plug  into 
the  hole  at  2  and  throwing  the  switch  to  the  left  so  as  to  make 


336 


ELECTRIC  IGNITION 


connection  between  the  contact-pieces  3  and  4,  referring  more 
particularly  to  Fig.  262,  the  current  from  the  magneto  terminal 
Ma  flows  through  the  connecting  wire  to  the  switch-point  4  and 
switch-blade  i.  The  current  divides  at  the  switch-blade  when 
the  interrupter  7-8  of  the  magneto  has  its  contact-points  together 


FIG.  262.     (See  also  Fig.  261.) 

Internal  and  External  Connections  of  Early  Form  of  Eisemann  High-tension 

Ignition  System. 

so  as  to  close  its  circuit.  Most  of  the  current  then  flows  through 
the  low-resistance  shunt  circuit  from  i  to  the  plug  in  2,  then  to  6 
and  on  through  the  connecting  wire  to  the  stationary  contact- 
point  7  of  the  interrupter  and  to  the  interrupter-lever  8,  which 
brings  it  to  the  grounded  end  of  the  armature  winding  10.  A 
small  portion  of  the  current  flows  from  i  to  the  switch-point  3 
and  on  to  12  and  the  primary  winding  of  the  spark-coil  1 1 ,  then 


HIGH-TENSION  DUAL  AND  COMBINED  IGNITION  SYSTEMS     337 

from  the  junction  of  the  two  windings  of  the  coil  to  the  terminal 
MB  and  on  to  ground  at  13,  thus  returning  to  the  ground  end 
of  the  armature  winding  of  the  magneto.  At  the  instant  that 
the  interrupter  breaks  the  shunt  circuit  by  separating  the  con- 
tact-points 7  and  8,  a  comparatively  large  current  is  sent  through 
the  primary  of  the  spark-coil  and  a  jump-spark  passes  between 
the  points  of  one  of  the  spark-plugs.  The  high-tension  terminal 
H  of  the  spark-coil  is  connected  to  the  rotor  14  of  the  distributer, 
which  is  of  the  usual  form. 

When  the  battery  is  in  circuit,  the  switch-blade  being  thrown 
to  the  right  to  make  contact  with  the  switch- point  5,  and  the 
plug  in  at  2,  the  magneto  armature  is  on  open  circuit.  Current 
flows  from  the  positive  (+)  side  of  the  battery  through  the 
connection  B-I2  to  the  primary  winding  of  the  spark-coil  and 
thence  through  MB  to  ground  at  13.  This  brings  it  to  the 
interrupter  lever  8,  from  which  it  passes  through  the  closed  con- 
tact-points to  the  stationary  contact-piece  7  and  thence  through 
R  to  the  switch  terminal  6,  then  through  the  plug  in  2  and  on 
through  the  switch-blade  i,  which  is  in  contact  with  5,  and  on 
to  the  negative  (— )  side  of  the  battery.  Interruption  of  the 
current  by  the  separation  of  the  contact-points  of  the  interrupter 
produces  a  spark  at  one  of  the  spark-plugs. 

The  condenser  9  is  in  parallel  with  the  interrupter  in  the  usual 
manner.  A  safety  spark-gap  is  shown  at  15. 

196.  Eisemann-Carpentier  Ignition  System.  —  Figs.  263  and 
264.  In  this  system  the  battery  has  its  own  timer  and  trembler 
spark-coil,  and  the  magneto  has  its  own  mechanically  operated 
interrupter  and  a  non-trembler  spark-coil.  The  same  distributer 
is  always  used  for  directing  the  high-tension  current  to  the  spark- 
plugs. The  two  spark-coils  are  inclosed  in  the  same  box,  which 
has  a  hand-switch  for  throwing  in  either  the  battery  or  the 
magneto,  or  for  cutting  both  out  of  circuit. 

The  movable  part  of  the  switch  is  represented  conventionally, 
in  Fig.  264,  as  a  piece  of  insulating  material  i  to  whose  ends  are 
fastened  two  metal  contact-pieces  2  and  3.  The  stationary 
contact-points  of  the  switch  are  4  and  5  for  the  battery  circuit, 
6  and  7  for  the  magneto  circuit,  and  8,  9,  and  10  for  the  high- 


ELECTRIC  IGNITION 


tension  circuits.  The  timer  is  of  the  form  common  to  battery 
ignition  systems  with  individual  spark-coils  of  the  trembler  type, 
but  is  modified  by  connecting  all  of  the  stationary  contact-points 
together  with  a  wire  16. 

The  switch  is  shown  set  for  using  battery  current.  The  path 
of  the  current  is  from  the  positive  (-h)  side  of  the  battery  to 
the  terminal  P  and  switch -pole  4,  through  2  to  5,  thence  to  the 
trembler  interrupter  n  and  primary  winding  of  transformer  17, 
from  which  it  flows  to  ground  by  the  path  12-13-14.  This 
brings  it  to  the  rotor  15  of  the  timer,  from  which  it  goes  to  the 


Timer 


Magneto 


FIG.  263.     (See  also  Fig.  264.) 
Eisemann-Carpentier  High-tension  Ignition  System. 

negative  (  — )  side  of  the  battery.  The  high-tension  current 
follows  the  path  from  the  secondary  terminal  19  to  the  switch- 
pole  8,  then  through  3  to  switch-pole  9,  thence  to  terminal  H 
and  on  to  the  rotor  21  of  the  distributer,  which  directs  it  to  the 
spark-plugs.  From  the  ground  side  of  the  spark-plug  the  high- 
tension  current  has  the  permanent  circuit  14-13-12  back  to  the 
spark-coil  17. 

When  the  switch  is  set  to  the  position  for  magneto  current, 
the  part  2  connects  the  poles  6  and  7,  and  the  part  3  connects 
poles  9  and  10.  The  magneto  is  of  the  interrupted  shunt-circuit 
type.  During  the  time  the  interrupter  parts  23  and  24  are  in 


HIGH-TENSION  DUAL  AND  COMBINED  IGNITION  SYSTEMS      339 

contact  with  each  other  (interrupter  closed)  most  of  the  armature 
current  flows  from  23  through  the  interrupter  lever  24  to  ground 
and  thence  to  the  grounded  end  of  the  armature  winding  25.  A 
small  portion  of  the  armature  current  flows  at  the  same  time 
from  23  through  the  path  22-MG  to  the  switch -pole  7,  then 


FIG.  264.     (See  also  Fig.  263.) 

Internal  and  External  Connections  of  Eisemann-Carpentier  High-tension  Ignition 

System. 

through  2  to  6  and  on  to  the  non- trembler  transformer  18, 
through  whose  primary  winding  it  flows,  and  then  to  ground  by 
the  path  12-13-14.  This  brings  it  to  the  grounded  end  of  the 
armature  winding.  At  the  instant  the  shunt  circuit  is  broken 
by  the  interrupter  of  the  magneto,  a  comparatively  large  current 
is  sent  through  the  transformer  circuit  just  followed  out,  and 


340  ELECTRIC  IGNITION 

a  spark  is  caused  to  jump  at  one  of  the  spark-plugs.  The  high- 
tension  current  goes  from  the  secondary  terminal  20  to  switch- 
pole  10,  then  through  the  metal  3  on  the  switch-bar  to  pole  9 
and  on  to  the  rotor  21  of  the  distributer. 

The  push-button  26  is  for  starting  the  motor  on  spark.  The 
switch  must  be  set  in  battery  position,  as  shown,  when  doing 
this,  and  the  timer  rotor  must  not  be  in  contact  with  any  of  the 
stationary  contacts  of  the  timer.  Pressing  the  push-button 
then  closes  the  battery  circuit  through  the  trembler  coil  17.  If 
the  rotor  of  the  timer  is  in  contact  with  one  of  the  stationary 
contact-pieces  of  the  timer  while  the  motor  is  standing  still,  the 
battery  circuit  is  then  closed  through  the  trembler  coil  when  the 
switch  is  in  the  position  shown. 

The  safety  spark-gap  27  is  for  protecting  the  trembler  coil  17, 
and  the  safety -gap  28  answers  the  same  purpose  for  coil  18. 

The  condenser  29  is  in  parallel  with  the  trembler  interrupter 
n,  and  condenser  30  is  in  parallel  with  the  interrupter  23-24  of 
the  magneto. 

The  rotor  of  the  timer  and  the  interrupter  of  the  magneto 
must  be  set  so  that  the  instant  of  ignition  will  not  be  greatly 
changed  by  switching  from  one  source  of  primary  current  to  the 
other. 

197.  Bosch  Dual  Ignition  System.  —  Fig.  265.  This  system 
operates  on  magneto  current  or  on  battery  current,  according 
to  the  position  of  the  switch.  It  comprises  a  high-tension  mag- 
neto having  two  interrupters  and  a  double-wound  armature  of 
the  rotary  shuttle  type,  a  transformer  spark-coil  in  conjunction 
with  a  switch,  a  battery,  and  jump-spark  igniters  as  its  chief 
elements.  Of  the  two  mechanically  operated  interrupters  in 
the  magneto,  one  is  for  the  battery  current  and  the  other  for 
magneto  primary  current.  The  transformer  coil  is  not  in  action 
while  the  system  is  operating  on  magneto  current. 

The  transformer  is  of  the  non-trembler  type,  so  far  as  its 
operation  while  the  motor  is  running  is  concerned,  but  it  has  a 
trembler  interrupter  to  be  used  for  starting  the  motor  on  spark. 
When  the  switch  is  in  battery  position,  pressing  the  push- 
button lightly  closes  the  battery  circuit  at  the  trembler  inter- 


HIGH-TENSION  DUAL  AND   COMBINED  IGNITION  SYSTEMS 


341 


rupter,  and  the  trembler  then  begins  to  vibrate  so  as  to  inter- 
rupt the  battery  current  through  the  spark-coil,  provided  the 
magneto  has  not  stopped  in  such  a  position  as  to  keep  the 
battery  circuit  closed  on  account  of  its  interrupter  contacts 
being  pressed  together.  But  if  the  battery  circuit  is  closed  in 
the  magneto,  as  just  stated,  then  a  harder  pressure  on  the  push- 
button, followed  immediately  by  release  of  pressure,  produces  a 
spark  at  the  igniter  at  the  instant  of  release  of  pressure. 


Spark-coil     Side  view 
and  Switch      of  coil 


Battery 
Sec.to  Dist. 
Mg.Sec.to  Switch 
Mg.Grounding  Wire 


FIG.  265.     (See  also  Figs.  266,  267,  and  268.) 
Bosch  Dual  High-tension  Ignition  System. 

The  interrupter  end  of  the  magneto  is  shown  in  Fig.  266.  In 
this  figure,  the  interrupter  for  the  current  generated  in  the  pri- 
mary winding  of  the  magneto  is  called  the  "  magneto  inter- 
rupter," and  that  for  interrupting  the  battery  current  is  called 
the  "  battery  timer."  Both  of  these  are  of  the  rocking-lever 
type. 

The  magneto  interrupter  rotates  with  the  magneto  armature. 
A  piece  of  fiber  in  one  end  of  the  lever  strikes  against  cam- 
lobes  so  that  a  rocking  movement  of  the  lever  is  produced  twice 


342 


ELECTRIC  IGNITION 


during  each  revolution  of  the  armature.  The  upper  end  of  the 
lever,  as  shown  in  the  illustration,  is  in  contact  with  one  of  the 
cam-lobes.  The  part  to  which  these  cam-lobes  are  attached  does 
not  rotate,  but  can  be  rocked  by  the  spark  control  to  vary  the 
time  of  ignition.  The  contact-piece  which  carries  the  "inter- 
rupter adjustment  "  is  connected  to  the  junction  of  the  primary 


OH    TENSION     CONNECTION 


FIG.  266. 
High-tension  Magneto  with  Two  Interrupters  for  Fig.  265. 

and  secondary  windings  of  the  armature  and  to  the  insulated 
"  short-circuiting  terminal,"  but  is  insulated  from  the  other  parts 
of  the  magneto.  The  interrupter-lever  of  the  magneto  inter- 
rupter is  electrically  connected  to  the  frame  of  the  magneto. 

The  battery  timer  does  not  rotate.  Its  interrupter-lever  is 
operated  by  a  two-lobed  steel  cam  which  revolves  with  the 
armature  of  the  magneto.  This  cam  is  in  the  form  of  a.  steel 
ring  with  outwardly  projecting  lobes.  The  interrupter-lever  of 


HIGH-TENSION  DUAL  AND  COMBINED  IGNITION  SYSTEMS     343 


the  battery  timer  is  electrically  connected  to  the  frame  of  the 
magneto.  The  "  timer  adjustment  "  and  the  "  battery  con- 
nection "  are  electrically  connected  together  and  are  insulated 
from  the  other  parts  of  the  magneto.  The  battery  timer  moves 
with  the  "  timing  control  arm  "  when  the  latter  is  rocked  to 
vary  the  time  of  ignition. 

The  "  high-tension  connection  "  is  in  permanent  electric  con- 
nection with  the  distributer  brush. 

The  beginning  of  the  primary  winding  of  the  armature  is 
electrically  connected  to  the  armature  core  and  thence  to  the 


FIG.  267.     (See  also  Fig.  268.) 
Transformer  Spark-Coil  and  Switch  for  Fig.  265. 

frame  of  the  magneto;  the  high-tension  end  of  the  secondary 
winding  is  connected  to  a  slip-ring  against  which  bears  a  brush 
that  is  carried  by  the  insulated  brush-holder  3,  Fig.  265.  There 
is  no  connection,  in  the  magneto,  between  the  high-tension 
winding  of  the  armature  and  the  distributer.  It  has  been 
stated  that  the  junction  of  the  two  armature  windings  is  con- 
nected to  the  insulated  part  of  the  magneto  interrupter. 

The  combined  spark-coil,  switch,  and  push-button  starter  are 
shown  assembled  in  Fig.  267.  The  coil  body,  the  connecting 
plate  of  the  switch,  and  the  protecting  cover  for  it  are  shown 


344 


ELECTRIC  IGNITION 


separately  in  Fig.  268.  The  switch  is  provided  with  a  lock  and 
removable  key,  by  means  of  which  it  can  be  locked  so  that  the 
ignition  system  cannot  be  used. 

When  the  switch  is  in  battery  position,  the  battery  circuit  is 
closed  at  the  coil,  and  the  high-tension  terminal  of  the  trans- 
former coil  is  connected  to  the  central  terminal  4  of  the  distrib- 
uter of  the  magneto.  The  short-circuiting  terminal  2  of  the 
magneto  is  also  connected  to  ground  through  the  switch  so  as 


FIG.  268. 
Parts  of  Fig.  267. 

to  prevent  the  induction  of  high  pressure  in  the  magneto  arma- 
ture, and  the  high-tension  terminal  3  of  the  magneto  is  on  open 
circuit  at  the  switch.  Under  this  condition  the  magneto  is  elec- 
trically inactive,  although  its  parts  move  mechanically  in  the 
usual  manner.  The  battery  timer  interrupts  the  battery  cur- 
rent, which  flows  through  the  primary  winding  of  the  spark- 
coil,  thus  inducing  high-tension  current  in  the  secondary  of  the 
spark-coil,  which  current  flows  to  the  distributer  brush  of  the 
magneto  and  is  distributed  to  the  spark-plugs. 

When  the  switch  is  in  magneto  position,  the  battery  circuit 
and  the  high-tension  circuit  of  the  spark-coil  are  both  open  at 


HIGH-TENSION  DUAL  AND  COMBINED  IGNITION  SYSTEMS      345 


the  switch,  thus  making  the  battery  circuit  inoperative.  The 
short-circuiting  circuit  is  open  at  the  switch,  and  the  high- 
tension  terminal  3  of  the  magneto  is  connected,  through  the 
switch,  to  the  distributer  terminal  4  of  the  magneto.  The 
magneto  then  generates  and  delivers  high-tension  current  to  the 
spark-plugs.  The  battery  timer  is  electrically  inoperative  under 
this  condition,  but  moves  mechanically  in  the  usual  manner. 

197.1.   Duplex  High-tension  Ignition  System  Having  a  Bat- 
tery in  Series  with  the  Primary  Winding  of  the  Magneto.  - 
The  complete  system  is  shown  in  Fig.  269.     Its  essential  parts 


.Kick  Coil 
and  Switch 


L  Keylock 

K  Kick  lever 

O  Off  position 

B  Battery  operating 

M  Magneto  operating 

P  Press  button 


FIG.  269.     (See  also  Figs.  270,  271,  and  272.) 
Bosch  Duplex  High-tension  Ignition  System. 

are  the  spark-plugs;  a  battery;  a  combined  kick-coil,  switch,  and 
push-button;  and  a  magneto  of  the  double- wound  shuttle-arm- 
ature type  provided  with  a  two-segment  commutator  and  com- 
mutator brushes  in  addition  to  the  mechanically  operated  inter- 
rupter. The  connections  between  the  magneto,  the  battery,  and 
the  kick-coil  are  shown  more  distinctly  in  Fig.  270.  The  kick- 
coil,  Fig.  271,  has  only  one  winding,  and  is  provided  with  a  key 
lock  for  preventing  the  use  of  the  ignition  system  while  the 
coil  is  locked.  The  interrupter  end  of  the  magneto  is  shown  in 
Fig.  272. 

The  switch  can  be  set  for  operating  the  magneto  system  on 
both  battery  and  magneto  current,  at  the  same  instant,  and  for 


346 


ELECTRIC  IGNITION 


operating  on  magneto  current  only.  The  real  purpose  of  the 
battery  is  to  supply  current  for  starting  the  motor,  either  on 
spark  by  using  the  push-button,  or  when  cranking  the  motor 
or  otherwise  driving  it  by  power  from  some  external  source. 

Referring  to  the  magneto,  Fig.  272,  the  beginning  of  the 
primary  winding  of  the  shuttle-wound  armature  is  grounded  to 
the  armature  core.  The  junction  of  the  two  windings  is  con- 
nected to  the  insulated  side  of  the  interrupter.  This  side  of  the 


6  Volt  Battery 

©  + 


Switeh.Plate  of  J 
Coil  1 


If  Engine  starts  but  will  not  continue  to  run 
reverse  the  battery  connections 

FIG.  270. 
Low-tension  Connections  for  Bosch  Duplex  Ignition  System. 

interrupter  has  the  means  of  adjustment  for  one  of  the  plat- 
inum contact-points.  The  high-tension  end  of  the  secondary 
winding  is  connected  to  the  distributer  brush  by  means  of  a 
slip-ring,  brushes,  and  other  suitable  connectors,  or  other  corre- 
sponding devices.  The  interrupter-lever  is  grounded  to  the  frame 
of  the  magneto. 

The  characteristic  feature  of  this  magneto  consists  of  a  two-seg- 
ment commutator  whose  insulated  segments  are  fastened  to  the 
inner  side  of  the  interrupter  cover,  and  a  pair  of  carbon  brushes, 
A  and  B,  which  make  sliding  contact  with  the  commutator. 


HIGH-TENSION  DUAL  AND   COMBINED  IGNITION   SYSTEMS     347 

Brush  A  is  carried  by  and  electrically  connected  to  the  insulated 
side  of  the  interrupter,  and  brush  B  is  electrically  connected  to 
the  grounded  lever  of  the  interrupter.  Each  commutator  seg- 
ment has  an  insulated  terminal  connected  to  it.  These  two 
terminals  are  on  the  outer  side  of  the  interrupter  cover.  They 
are  numbered  i  and  2  in  Figs.  269  and  270. 

When  the  switch  is  set  in  its  battery-magneto  position,  one 
side  of  the  battery  is  connected  to  terminal  i  of  the  commutator, 
and  the  other  side  of  the  battery  is  connected  to  terminal  2  of 


FIG.  271. 
Single-wound  Kick-Coil  for  Fig.  269. 

the  commutator.  As  shown  in  Fig.  270,  the  positive  (+)  side 
of  the  battery  is  permanently  connected  to  terminal  i  of  the  com- 
mutator, and,  when  the  switch  is  in  battery-magneto  position, 
the  negative  (  — )  side  of  the  battery  is  connected  to  terminal  2 
of  the  commutator.  Then,  while  the  armature  is  standing  still 
with  brush  A  in  contact  with  the  commutator  segment  to 
which  terminal  i  is  connected,  and  carbon  brush  B  in  contact 
with  the  commutator  segment  connected  to  terminal  2,  current 
flows  from  the  positive  side  of  the  battery  to  brush  A ,  thence  in 
parallel  through  the  interrupter  contacts  and  the  primary  of  the 


348  ELECTRIC  IGNITION 

armature  in  parallel  while  the  interrupter  contacts  are  together, 
or  through  the  primary  of  the  armature  alone  while  the  inter- 
rupter contacts  are  separated,  to  brush  B  and  the  commutator 
segment  connected  to  terminal  2,  and  on  back  through  the 
switch  to  the  negative  side  of  the  battery.  The  current  thus 
flows  into  the  insulated  end  of  the  primary  of  the  armature  and 
out  of  the  grounded  end  of  the  primary,  while  the  conditions 
are  as  just  described.  The  ohmic  resistance  of  the  kick-coil 
limits  the  battery  current  to  a  safe  amount.  When  the  arma- 
ture and  the  interrupter  have  been  rotated  to  a  position  to 
bring  the  brush  B  into  contact  with  the  segment  connected  to 
terminal  i,  and  brush  A  into  contact  with  the  segment  con- 
nected to  terminal  2,  then,  while  the  armature  is  at  rest,  the 
battery  current  flows  through  the  armature  primary  in  the 
opposite  direction.  By  quickly  separating  the  closed  contacts 
of  the  interrupter  while  battery  current  is  flowing  through  them, 
the  consequent  interruption  of  the  battery  current  sends  a 
sudden  impulse  of  battery  current  through  the  primary  of  the 
armature  so  as  to  induce  an  electromotive  force  in  the  secondary 
high  enough  to  produce  a  spark  at  the  igniter.  The  reaction 
of  the  kick-coil  helps  to  make  the  impulse  current  sufficiently 
large.  The  direction  of  flow  of  this  impulse  current  is  the  same 
as  that  of  the  small  amount  of  battery  current  that  flows  through 
the  primary  before  the  contact-points  are  separated. 

If  the  battery  current  is  now  cut  off,  either  by  disconnecting 
one  of  the  battery  wires,  or  by  moving  the  switch  to  its  magneto 
position,  both  of  which  have  the  same  effect,  then  rotating  the 
magneto  armature  induces  an  alternating  current  in  its  primary 
winding.  The  direction  of  flow  of  this  generated  primary  cur- 
rent at  any  instant  is  opposite  that  which  the  battery  current 
had,  as  just  described.  The  interruption  of  the  generated  cur- 
rent produces  a  spark  at  the  igniter  when  the  speed  of  rotation 
of  the  armature  is  sufficiently  high. 

While  the  switch  is  in  its  battery-magneto  position,  so  that 
the  battery  is  connected  to  the  magneto  as  has  been  described, 
then  the  electromotive  force  generated  in  the  armature  primary 
by  the  rotation  of  the  armature  opposes  the  tendency  of  the 


HIGH-TENSION  DUAL  AND  COMBINED  IGNITION  SYSTEMS      349 

battery  to  send  current  through  the  armature  primary.  While 
the  rotative  speed  of  the  armature  is  extremely  slow,  the  battery 
current  predominates  in  the  armature  winding.  The  ignition 
spark  under  this  condition  is  due  to  the  interruption  of  the 
portion  of  the  battery  current  that  flows  through  the  contact- 
points. 

At  some  speed  of  the  armature  slightly  higher  than  that  just 
mentioned,  and  at  the  instant  the  contact-points  just  begin  to 
separate,  the  generated  electromotive  force  in  the  armature 
primary  just  balances  the  tendency  of  the  battery  to  send 
current  through  the  armature  primary.  There  is  consequently 
no  flow  of  current  in  the  armature  primary  at  the  instant  of 
interruption  of  the  battery  current,  all  of  which  flows  through 
the  contact-points  just  before  its  interruption.  Under  this 
condition  the  ignition  spark  is  due  to  the  interrupted  battery 
current. 

At  high  speeds  of  rotation,  the  electromotive  force  generated 
in  the  armature  primary  sends  a  current  through  the  primary 
in  the  direction  opposite  that  in  which  the  battery  current 
flows  through  it  while  the  armature  is  not  rotating,  or  is  rotat- 
ing at  extremely  slow  speed.  This  generated  current  and  the 
battery  current  flow  together  in  the  same  direction  through  the 
contact-points  of  the  interrupter  just  before  the  contact-points 
are  separated.  The  separation  of  the  contact-points  then  stops 
the  flow  of  the  generated  current  through  the  armature  primary 
and  sends  an  impulse  of  battery  current  through  the  primary 
in  the  direction  opposite  that  in  which  the  generated  current 
was  flowing.  This  sudden  decrease  of  generated  current  and 
increase  of  battery  impulse  current  is  in  effect  a  reversal  of 
current  in  the  primary,  and  it  induces  pressure  in  the  secondary 
of  the  armature  sufficient  to  make  an  ignition  spark  at  the 
igniter. 

At  ordinary  operating  speeds  of  the  magneto  the  electro- 
motive force  induced  in  the  armature  primary  reduces  the  bat- 
tery current  to  an  amount  less  than  that  which  flows  while  the 
armature  is  at  rest  or  rotating  at  slow  speed.  Therefore,  even 
though  the  switch  is  left  in  battery-magneto  position  while 


350 


ELECTRIC  IGNITION 


COMMUTATOR    SEGMENTS 


FIG.  272. 
Bosch  Duplex  Magneto  for  Fig.  269. 


HIGH-TENSION  DUAL  AND  COMBINED  IGNITION  SYSTEMS      351 

running,  the  battery  does  not  deliver  much  current,  and  the 
operation  of  the  system  is  chiefly  on  magneto  current. 

When  the  switch  is  set  in  its  magneto  position,  the  battery  is 
cut  out  of  circuit  completely. 

In  the  off  position  of  the  switch  the  battery  is  cut  out  and 
the  wires  between  the  magneto  and  the  switch  are  connected 
together  at  the  switch,  thus  short-circuiting  the  magneto  pri- 
mary so  as  to  prevent  the  interruption  of  the  primary  current 
and  the  generation  of  pressure  in  the  magneto  high  enough  to 
cause  an  ignition  spark. 

Pressing  the  push-button  while  the  switch  is  in  its  battery- 
magneto  position  breaks  the  battery  circuit  provided  the  arma- 
ture of  the  magneto  is  in  such  a  position  that  the  contacts  of 
the  interrupter  are  separated.  The  sudden  stoppage  of  cur- 
rent thus  caused  in  the  magneto  primary  induces  a  pressure  in 
the  secondary  that  forces  a  spark  across  the  spark-gap  of  the 
igniter.  But  if  the  interrupter  contacts  are  together  so  as  to 
close  the  circuit  through  them,  then,  although  pressing  the 
button  breaks  the  battery  circuit  and  stops  the  flow  of  current, 
no  ignition  spark  is  produced.  This  is  because  the  amount  of 
battery  current  that  flows  through  the  magneto  primary  while 
the  interrupter  contacts  are  together  is  so  small  that  it  will  not 
produce  an  ignition  spark  when  it  is  interrupted. 

If  the  battery  is  connected  to  the  magneto  in  the  reverse 
manner  from  that  shown,  so  that  the  positive  (+)  side  of  the 
battery  is  connected  to  terminal  2  of  the  magneto,  and  the 
battery  negative  (  — )  to  terminal  i,  then,  although  the  motor 
can  be  started  by  pressing  the  push-button  or  by  slow  rotation 
of  the  motor  and  the  magneto,  ignition  will  cease  as  soon  as  the 
motor  gains  some  speed,  the  switch  still  remaining  in  battery- 
magneto  position.  This  is  because  the  battery  current  and  the 
current  generated  in  the  magneto  primary  flow  in  the  same 
direction  through  the  primary.  Under  this  condition  the 
amount  of  current  flowing  through  the  interrupter  contacts  at 
the  instant  their  separation  begins  is  not  sufficient  to  produce  an 
ignition  spark  when  the  current  through  the  contact-points  is 
interrupted. 


352  ELECTRIC  IGNITION 

198.  Magneto  with  Two  High-tension  Windings  for  Dual 
Ignition.  —  In  this  system,  one  of  the  two  high-tension  windings 
of  the  magneto  is  used  in  connection  with  its  own  set  of  spark- 
plugs, and  the  other  high-tension  winding  with  its  own  set  of 
spark-plugs.  Two  ignition  plugs  are  put  in  each  combustion 
chamber  and  are  caused  to  spark  at  the  same  instant  on  high- 
tension  current  from  the  magneto.  One  of  these  plugs  is  con- 
nected to  one  of  the  high-tension  windings  of  the  magneto,  and 
the  other  plug  to  the  other  high-tension  winding.  The  two 
plugs  thus  receive  current  from  different  windings.  The  inter- 
ruption of  the  current  in  the  primary  winding  of  the  magneto 
armature  induces  the  sparks  at  the  two  plugk  in  the  same  com- 
bustion chamber  at  the  same  instant,  as  stated. 


CHAPTER  XXII. 

HIGH-FREQUENCY  ALTERNATING-CURRENT  MAGNETOS. 

199.  Introductory.  —  The  high-frequency  magnetos  described 
in  this  chapter  can  be  substituted  for  the  battery  in  battery 
ignition  systems  which  have  a  trembler  spark-coil  and  a  timer 
for  closing  the  low-tension  circuit  at,  or  slightly  before,  the 
instant  of  ignition,  provided  the  trembler  of  the  spark-coil  is 
one  that  has  a  high  rate  of  vibration.     The  trembler  must  be 
sensitive.     In  some  such  ignition  systems  a  battery  is  used  for 
starting,  and  the  magneto  is  then  switched  on  to  supply  the 
low-tension  current.     The  battery  is  cut  out  when  the  magneto 
is  switched  on.     The  magneto  does  not  of  necessity  rotate  in 
synchronism  with  the  motor,  and  can  therefore  be  driven  by  a 
belt  or  other  form  of  friction  drive.     The  magneto  is  run  at  a 
speed  high   enough  to  generate   a  low-tension  current  whose 
alternations  are  rapid  enough  to  cause  only  a  slight  variation 
in  the  instant  of  ignition  so  far  as  affected  by  lack  of  synchronism 
between  the  rotation  of  the  magneto  and  motor.     The  rapidity 
of  alternation  of  the  current  is  limited  by  the  degree  of  prompt- 
ness with  which  the  trembler  responds  to  the  magnetic  attraction 
caused  by  the  flow  of   current  through  the  spark-coil.     The 
inductive  resistance  of  the  spark-coil  is  also  a  factor  to  be  con- 
sidered in  determining  how  rapidly  the  current  can  alternate. 

Magnetos  of  this  type  have  the  advantage  of  being  extremely 
simple  in  form  and  inexpensive. 

200.  The  W.  &  S.  magneto  is  shown  in  Fig.  273  in  complete 
form.     Figs.  274,  275,  and  276  show  groups  of  different  parts 
of  the  magneto.     Fig.  277  gives  the  positions  of  the  inductor 
arms  relative  to  each  other;  also  the  path  of  magnetic  flux. 

The  armature  winding  C  is  a  single  spiral  coil  of  insulated 
copper  wire  with  terminals  at  D  and  Di.  This  stationary  coil 
encircles  the  neck  between  the  two  rotary  inductor  spiders  A 

353 


354 


ELECTRIC  IGNITION 


and  B,  each  of  which  has  three  arms.  These  spiders  are  pinned 
to  a  shaft  K  which  runs  on  two  ball  bearings  and  is  driven  by  a 
belt  on  the  pulley  E.  One  of  the  ball  bearings  is  indicated  by 


FIG.  273.     (See  also  Figs.  274,  275,  276, 
and  277.) 

High-frequency  Low-tension  Magneto  with 
Stationary  Armature  and  Rotary  In- 
ductor. Wheeler  &  Schebler,  Indianap- 
olis, Indiana. 


FIG.  274. 

Parts  Remaining  after  Magnets  are 
Removed  from  Fig.  273. 


the  letter  M.     The  bearing  farthest  from  the  pulley  is  supported 
by  the  end-piece  P.     The  pole -pieces  F  and  Fi  are  separated  by 


FIG.  275. 
Inductor,  Pulley  and  Spirally-wound  Armature  of  Fig.   273. 

the  aluminum  piece  G  (non-magnetic)  and  are  fastened  to  the 
non-magnetic  base  H.  The  only  moving  part  of  the  magneto 
is  the  rigidly  connected  group  made  up  of  the  inductor  spiders, 
the  pulley,  and  the  shaft  upon  which  they  are  mounted. 


HIGH-FREQUENCY  ALTERNATING-CURRENT  MAGNETOS      355 


FIG.  270. 
End  View  of  Fig.  274. 


In  Fig.  277  the  spider  with  the  arms  Ai,  A2,  and  A$  is  in 

front  of  the  armature  coil  C,  and  the  spider  with  the  arms  Bi, 

B2,  and  £3  is  in  the  rear  of 

the  coil.     It  can  be  seen  that 

the   arms   of  one    spider   lie 

opposite  the  angles  between 

the  arms  of  the  other.     While 

the  inductor  is  in  the  position 

shown  in  Fig.  277,  the  path  of 

magnetic  flux  is  from  N  along 

the  broken  line  L,  through  the 

arm  Ai,  then  back  through 

the  neck  of  the  inductor  (and 

the  opening  of  the  coil)  to  the 

rear  spider  and  out  through 

the  arm  Bi  to  S.    When  the 

inductor  has  rotated  one- 
twelfth  of  a  revolution  there 

is  no  magnetic  flux  through  the  neck  between  the  two  spiders. 

One  of  the  spiders  is  then  in  the  position  shown  in  Fig.  276, 

neglecting  the  lettering  of  this 
figure.  When  the  inductor  has 
revolved  clockwise  one-sixth 
of  a  revolution  from  the  posi- 
tion shown  in  Fig.  277,  so  as 
to  bring  the  arm  B2  opposite 
the  pole-piece  Fi,  and  A\ 
opposite  Fj  then  the  magnetic 
flux  is  from  Nmto  the  inductor 
arm  B2  and  forward  through 
the  inductor  neck  to  the  spider 
A ,  then  out  through  arm  A  i 
to  S.  Similar  changes  of  flux 
occur  twice  more  during  the 
FIG.  277.  remainder  of  the  revolution. 

Outline  of  Fig.  273.  xhe  result  is  that  six  impulses 

of  current  are  generated  during  one  revolution  of  the  inductor. 


356 


ELECTRIC  IGNITION 


The  rotative  speed  of  the  inductor  should  be  about  three 
times  that  of  the  motor  crank-shaft  for  high-speed  motors,  and 
at  a  higher  relative  speed  for  slow-speed  motors. 

201.  K-W  High-frequency  Magneto.  —  This  magneto  has  a 
stationary  spiral-wound  armature  coil  and  a  rotary  inductor 
with  four  arms.  Fig.  278  is  an  exterior  view  of  the  type  that 


FIGS.  278  and  279.     (See  also  Figs.  280  and  281.) 

Two  Forms  of  K-W  High-frequency  Magneto  with  Stationary  Armature  and 
Rotary  Inductor.    The  K-W  Ignition  Company,  Cleveland,  Ohio. 

has  the  armature  and  inductor  at  the  bottom  when  the  machine 
is  set  in  the  position  that  is  in  accordance  with  its  design.  Fig. 
279  is  designed  to  operate  with  the  armature  and  inductor  at 
the  top.  The  internal  construction  is  shown  in  Fig.  280.  One 
of  the  straight  bars,  each  of  which  forms  two  arms  of  the  rotary 
inductor,  is  shown  with  its  crowned  end  A  nearest  to  the  observer. 
The  other  bar  of  the  inductor  has  its  end  B  nearest  to  the  ob- 
server. These  bars  are  laminated.  They  are  mounted  on  a  shaft 


HIGH-FREQUENCY  ALTERNATING-CURRENT  MAGNETOS      357 


FIG.  280. 
View  showing  Armature  and  Inductor  of  Figs,  278  and  279. 

and  joined  together  by  a  large  neck  that 
is  encircled  by  the  armature  coil  C. 
The  two  arms,  A  and  B,  of  the  inductor 
are  at  right  angles  to  each  other,  as 
shown  in  Fig.  281.  This  figure  also 
shows  the  position  of  the  armature  and 
inductor  relative  to  the  pole-pieces  N 
and  S  of  the  magnets. 

The  action  of  this  machine  in  generat- 
ing a  current  is  similar  to  that  of  the 
W.  &  S.  magneto  that  has  been  described, 
except  that  the  K-W  machine  produces 
four  impulses  per  revolution  of  the  in- 
ductor, instead  of  six. 

The  armature  and  the  inductor  are 
inclosed  in  a  cylindrical  case  which  is 
practically  water-tight. 

The  makers  recommend  a  speed  from 
two  and  a  half  to  three  times  that  of 
the  crank-shaft  of  a  high-speed  motor. 
For  low-speed  motors  the  magneto 
should  have  a  higher  speed  as  compared 
with  that  of  the  motor  crank-shaft.  It  should  not  run  much 
slower  than  for  the  high-speed  motor. 


FIG.  281. 

Outline  of  Field-magnets, 
Armature  and  Inductor 
of  Figs.  278  and  279. 


358 


ELECTRIC  IGNITION 


FIG.  282. 
(See  also  Figs.  283,  284,  and  285.) 

Armature  of  Ford  High-frequency 
Magneto. 


202.   The  Ford  high-frequency  magneto  has  several  spool- 
shaped  armature  coils  spaced  at  equal  distances  in  a  circle,  with 

the  axes  of  the  spools  all  parallel 
to  each  other  and  to  the  axis  of 
rotation  of  the  inductor.  Fig.  282 
shows  sixteen  spools  mounted  in 
this  manner  with  their  windings 
connected  so  that  the  coils  are  in 
series  with  each  other.  One  pair 
of  coils  are  not  connected  to  each 
other,  but  the  ends  of  the  windings, 
one  end  for  each  coil,  are  left  free 
for  terminals.  The  inductor  has 
several  V-shaped  magnets  such  as 
shown  in  Fig.  283.  Sixteen  of  these 
magnets  are  bolted  to  the  flywheel 
of  the  motor,  with  the  angle  of  the 
V  next  to  the  center  of  the  flywheel,  as  shown  in  Fig.  284.  The 
north  poles  of  the  magnets  are  placed  next  to  each  other, 
and  the  south  poles  likewise  next  to  each  other.  The 
magnets  rest  on  a  non-magnetic  ring  at  about  one-third 

of  the  length  of  the  magnets  in 
from  their  outer  ends.  The 
complete  assembly  is  shown  in  -pic.  283. 
Fig.  285,  together  with  someOneofthe 
of  the  transmission  mechanism  V-shaped 
of  an  automobile.  The  spools  Magnets 

,         ,,  ,.  used  in 

are  mounted  on  the  stationary    Fi    2g 
casing  that  incloses  the  fly- 
wheel and  plane  tary  change-speed  gears . 
Sixteen  electric   impulses    are   pro- 
duced during  each  revolution  of   the 
flywheel  (inductor)  when  that  number 
of  coils  and  of  magnets  are  used.     The 


FIG. 


Rotary  Magnet  Inductor 
for  Fig.  285. 


current  is  passed  through  a  trembler  spark-coil  in  the  usual  man- 
ner, a  timer  being  used  to  close  the  low-tension  (magneto)  circuit 
just  before  the  instant  that  ignition  is  to  occur  in  the  motor. 


HIGH-FREQUENCY  ALTERNATING-CURRENT  MAGNETOS      359 

While  the  rotor  of  the  magneto  is  in  such  a  position  that  the 
magnet-poles  are  opposite  the  ends  of  the  coils,  as  shown  in 
Fig.  285,  then,  taking  any  three  consecutive  coils,  A,  B,  C,  of 
which  the  middle  coil  B  is  opposite  the  north  poles  of  two  adja- 
cent magnets,  i  and  2,  the  S  pole  of  i  opposite  A,  and  the  S 
pole  of  2  opposite  C,  the  magnetic  flux  is  as  follows:  From  the 


FIG.  285.     (See  also  Figs.  282,  283,  and  284.) 
Ford  High-frequency  Low-tension  Magneto  Embodied  with  Other  Parts. 

two  N  poles  through  the  coil  B  to  the  casing  which  carries  the 
coils.  The  flux  then  divides  and  goes  in  opposite  directions 
through  the  casing  to  the  cores  of  A  and  C.  The  portion  which 
goes  to  A  then  goes  through  the  core  of  that  coil  to  the  S  pole 
of  magnet  i  and  on  through  the  bar  of  magnet  i  back  to  its  N 
pole.  In  a  similar  manner,  the  portion  that  goes  to  coil  C  goes 
through  the  core  of  C  to  the  5  pole  of  magnet  2  and  thence 
through  the  bar  of  2  back  to  the  N  pole. 

When  the  inductor  has  rotated  half  the  distance  between  the 
centers  of  two  adjacent  coils,  so  as  to  bring  the  magnet  poles 
opposite  the  spaces  between  the  coils,  then  there  is  no  magnetic 
flux  through  the  cores  of  the  coils.  When  the  inductor  has 


360  ELECTRIC  IGNITION 

rotated  from  its  first-mentioned  position  through  a  distance 
equal  to  that  between  the  centers  of  two  adjacent  coils,  so  as  to 
bring  the  magnet-poles  opposite  the  coils  again,  the  magnetic 
flux  through  the  cores  of  the  coils  will  be  in  the  opposite  direction 
from  that  for  the  first  position  mentioned. 


CHAPTER  XXIII. 
VARYING  THE  TIME   OF  IGNITION.     MULTIPLE  IGNITION. 

203.  Advancing  the  Timer  on  Account  of  Lag  in  the  Ignition 
Apparatus.  —  It  has  been  stated,  in  connection  with  ignition 
systems  which  comprise  a  trembler  interrupter,  that,  in  vari- 
able-speed motors,  the  timer  must  be  moved  so  as  to  interrupt 
the  primary  current  earlier  in  the  stroke  of  the  piston  when  the 
speed  of  rotation  of  the  motor  crank-shaft  is  high  than  when  it 
is  low.  The  reason  that  was  given  for  the  necessity  of  thus 
advancing  the  timer  was  that  there  is  a  certain  amount  of  lag 
in  the  operation  of  the  ignition  apparatus  after  the  timer  has 
closed  the  primary  circuit,  which  lag  covers  the  time  interval 
between  the  instant  of  closing  the  primary  circuit  by  the  timer 
and  the  jumping  of  a  spark  between  the  ignition  points  of  the 
igniter. 

Since  the  time  interval  of  lag,  measured  as  a  fraction  of  a 
second,  is  constant  whatever  the  rotative  speed  of  the  motor, 
the  rotative  movement  of  the  crank-shaft  of  the  motor  during 
the  period  of  lag  is  greater  when  the  motor  is  running  fast  than 
when  it  is  running  slowly.  If  the  timer  is  set  so  that  the  spark 
jumps  while  the  crank-shaft  is  in  its  dead-center  position  when 
the  motor  is  rotated  very  slowly,  as  when  turning  it  by  exterior 
power  for  starting  it,  then  the  spark  will  not  jump  till  after  the 
crank-shaft  has  passed  its  dead-center  position  when  the  motor 
begins  to  run  on  its  own  power.  The  angular  movement  of  the 
crank-shaft  from  its  dead-center  position  to  its  position  when  the 
spark  jumps  will  be  greater  when  the  rotative  speed  is  high  than 
when  it  is  low.  Thus,  at  1000  revolutions  per  minute,  the  crank- 
shaft will  move  twice  as  far  beyond  its  dead-center  position 
before  the  spark  jumps  as  it  will  when  rotating  at  500  revolu- 
tions per  minute.  The  lag  of  the  spark  is  proportional  to  the 
rotative  speed  of  the  motor  when  the  timer  remains  at  the  same 

361 


362  ELECTRIC  IGNITION 

position.  In  order  to  have  the  ignition  spark  jump  at  the  in- 
stant the  crank-shaft  is  passing  through  its  dead-center  position, 
the  timer  must  be  advanced  as  the  speed  of  the  motor  increases. 
The  amount  of  this  advance  is  proportional  to  the  speed  of  the 
motor,  if  the  initial  position  of  the  timer  is  that  which  gives  a 
spark  at  dead-center  position  of  the  crank-shaft  when  the  latter  is 
rotated  at  a  very  slow  speed  by  exterior  power,  as  has  been  stated. 

In  ignition  systems  whose  interrupter  is  mechanically  oper- 
ated, the  lag  is  much  less  than  in  one  operating  with  a  trembler 
interrupter.  Mechanical  interrupters  of  the  types  ordinarily 
used  on  magnetos  entirely  eliminate  mechanical  lag.  This  is 
also  substantially  true  of  other  forms  of  mechanical  interrupters 
in  which  the  moving  part  which  causes  the  interruption  of  the 
current  is  moved  by  a  spring  to  cause  the  interruption,  pro- 
vided the  spring-actuated  part  is  of  light  weight  and  moved  by 
a  spring  powerful  enough  to  produce  a  very  rapid  movement. 

In  ignition  systems  operating  with  a  trembler  interrupter, 
the  movement  of  the  spark-control  lever  to  advance  the  timer, 
ordinarily  called  "  advancing  the  spark/'  does  not  actually  ad- 
vance the  time  at  which  the  ignition  spark  jumps  relative  to 
the  movement  of  the  piston  when  the  rotative  speed  of  the 
motor  is  increasing,  unless  the  advance  of  the  timer  is  sufficient 
to  more  than  counterbalance  the  effect  of  the  increasing  speed. 

The  advance  of  the  timer  in  trembler-interrupter  ignition 
systems  must  be  greater  than  in  those  with  mechanically  oper- 
ated interrupters.  This  is  in  accordance  with  the  facts  that 
have  just  been  stated. 

204.  Variation  of  the  Time  of  Ignition  Relative  to  the  Rate 
of  Combustion  of  the  Charge  in  the  Motor.  —  This  can  be  most 
conveniently  discussed  first  in  connection  with  motors  which 
run  at  a  constant  speed. 

The  rate  of  burning  (combustion,  explosion)  of  the  charge  in 
the  motor  cylinder  varies  in  accordance  with  the  composition  of 
the  combustible  mixture  and  the  intensity  of  compression. 

There  is  a  certain  proportion  of  air  and  fuel,  for  each  kind  of 
fuel,  that  burns  more  rapidly  than  a  mixture  containing  either 
a  greater  or  less  proportion  of  fuel.  The  mixture  which  has 


VARYING  THE  TIME  OF  IGNITION  363 

the  highest  rate  of  combustion  may  be  called  the  normal  mix- 
ture for  that  particular  fuel.  The  proportions  of  air  and  fuel 
in  the  normal  mixture  are  different  for  the  different  kinds  of 
fuel,  and  the  rate  of  burning  is  in  general  different  for  the  nor- 
mal mixture  of  each  kind 'of  fuel.  In  general,  a  normal  mixture 
which  has  a  high  heating  value  has  a  higher  rate  of  burning 
than  a  normal  mixture  which  has  a  lower  heating  value.  There 
are  apparently  exceptions  to  this  statement,  however,  since 
some  of  the  permanent  gases  used  in  combustion  motors  have  a 
higher  rate  of  combustion  than  others. 

If  a  stationary  engine  operating  on  producer  gas  has  its 
ignition  properly  timed  for  a  normal  mixture  while  the  producer 
is  delivering  rich  gas  (of  high  heating  capacity  for  that  kind  of 
gas),  and  the  gas  then  becomes  lean  (of  less  heating  capacity) 
after  the  manner  of  operation  of  producers,  the  combustible 
mixture  going  into  the  engine  will  then  become  lean  if  the  setting 
of  the  proportioning  device  remains  unchanged.  The  ignition 
will  then  have  to  be  advanced  to  secure  the  most  efficient  re- 
sults for  the  kind  of  mixture  then  received.  This  is  because  the 
lean  mixture  is  slower  burning  than  the  normal  mixture,  and 
unless  it  is  ignited  earlier  than  the  normal  mixture,  combustion 
will  be  completed  too  late  in  the  stroke  of  the  piston  to  secure 
the  maximum  impulse  effect  against  the  piston  to  drive  it.  In 
the  same  manner,  if  the  ignition  is  properly  timed  for  normal 
mixture  when  the  producer  is  delivering  lean  gas,  the  ignition 
will  have  to  be  advanced  if  the  gas  coming  from  the  producer 
becomes  very  much  richer  and  the  setting  of  the  gas-propor- 
tioning device  is  not  changed.  In  this  case  the  over-rich  mix- 
ture is  slower  burning  than  the  leaner  normal  mixture.  The 
variation  of  the  timing  is  not  so  great  in  the  latter  case,  however, 
as  when  the  change  is  from  a  normal  mixture  using  rich  gas  to  lean 
gas.  Upon  setting  the  proportioning  device  so  as  to  obtain  a 
normal  mixture  with  the  rich  gas,  the  ignition  should  be  retarded. 

Relative  to  variation  in  the  intensity  of  compression  of  the 
combustible  charge,  ignition  must  be  advanced  when  the  com- 
pression is  reduced,  in  order  to  secure  the  maximum  amount 
of  power  from  the  charge  ignited.  Some  engines,  while  operat- 


364  ELECTRIC  IGNITION 

ing  on  a  normal  mixture  made  from  gas  of  a  constant  com- 
position, are  regulated  to  meet  the  varying  demand  for  power 
by  admitting  to  the  cylinder  an  amount  of  mixture  approxi- 
mately proportional  to  the  power  which  the  engine  is  called 
upon  to  deliver.  If  an  engine,  governed  to  approximately  con- 
stant speed  in  this  manner,  is  operating  on  full  load  with  its 
ignition  properly  timed,  then  if  the  load  falls  off  so  as  to  be- 
come light,  the  ignition  must  be  advanced  on  account  of  the 
reduced  compression  and  consequent  lower  rate  of  combustion. 
When  the  full  load  comes  on  again,  the  ignition  must  be  re- 
tarded to  its  initial  position.  This  refers  to  the  time  of  igni- 
tion for  obtaining  the  maximum  efficiency  in  the  use  of  the  fuel. 

The  above  statements,  modified  to  suit  the  conditions,  are 
applicable  to  motors  using  liquid  fuel. 

205.  Varying  the  Time  of  Ignition  with  Variation  of  Speed.  - 
Since  the  combustible  mixture  takes  an  appreciable  amount  of 
time  to  burn,  or  explode,  in  the  motor  cylinder,  it  must  be 
ignited  earlier  in  the  movement  of  the  piston  when  the  motor 
is  running  at  high  speed  than  at  low  speed,  in  order  to  obtain 
the  maximum  amount  of  power  from  the  fuel  consumed. 

The  extent  of  the  variation  of  the  time  of  ignition  in  accord- 
ance with  the  variation  of  speed  depends  on  the  kind  of  ignition 
cystem  used  and  the  location  of  the  igniter,  or  igniters,  in  the 
combustion  chamber.  An  ignition  system  which  gives  a  spark 
of  constant  strength  regardless  of  the  speed  of  rotation  of  the 
motor  must  have  the  time  of  ignition  varied  more  with  varia- 
tion of  speed  than  is  the  case  for  a  system  which  gives  a  stronger, 
or  hotter,  spark  as  the  speed  of  rotation  of  the  motor  increases. 
If  the  igniter  is  located  away  from  the  body  of  the  mixture  in 
the  combustion  chamber,  as  in  the  pocket  over  the  valve,  or 
between  the  valves,  of  some  types  of  motors,  then  the  ignition 
must  be  more  advanced  than  when  the  ignition  spark  is  made 
nearer  to  the  center  of  the  volume  of  the  charge. 

Most  ignition  systems  operating  on  battery  current  give  a 
spark  whose  strength  is  the  same  whatever  the  speed  of  the  motor. 
On  the  other  hand,  most  magneto  ignition  systems  using  cur- 
rent direct  from  the  magneto  give  a  stronger  spark  as  the  speed 


VARYING  THE  TIME  OF  IGNITION  365 

of  the  motor,  and  consequently  that  of  the  magneto,  increases. 
Less  advance  of  the  spark  is,  therefore,  required  in  magneto 
systems  of  this  nature  than  in  battery  systems.  This  state- 
ment applies  to  the  actual  occurrence  of  the  ignition  spark,  or 
arc,  and  is  not  intended  to  include  the  lag  which  occurs  in  a 
system  operating  with  a  trembler  interrupter.  The  lag  due  to 
the  trembler  makes  additional  advance  of  the  timer  necessary. 

206.  Reduction  of  Variation  of  Ignition  by  the  Use  of  Two 
Simultaneous  Ignition  Sparks.  —  It  is  common  practice  in  gas 
engines  of  large  size  to  have  two  or  more  simultaneously  oper- 
ated igniters  in  each  combustion  chamber.  These  are  generally 
located  some  distance  apart  and  in  such  positions  as  to  have  at 
least  one  of  them  in  the  part  of  the  combustion  chamber  where 
the  mixture  is  such  as  to  be  easily  ignited  when  there  is  a  re- 
duction in  the  amount  of  gas  admitted  on  account  of  light 
demand  for  power.  Aside  from  the  greater  certainty  of  pro- 
ducing ignition  of  the  charge,  the  use  of  igniters  at  more  than 
one  place  decreases  the  time  required  for  combustion  when 
ignition  occurs  at  more  than  one  locality.  This  is  due  to  the 
fact  that  each  of  the  propagating  flames  emanating  from  the 
points  of  ignition  has  a  less  distance  to  travel  when  ignition  is 
at  more  than  one  point  than  when  it  is  at  only  one  point.  The 
whole  charge  becomes  inflamed  quicker  when  ignited  at  two 
widely  separated  points  than  when  ignited  at  one  point  only. 
Since  combustion  is  completed  more  rapidly  with  ignition  at 
two  or  more  points,  there  is  less  movement  of  the  piston  and 
crank-shaft  during  combustion,  and  consequently  less  advance 
of  ignition  is  required.  This  means  that  there  is  less  variation  of 
the  time  of  ignition  under  different  conditions  of  the  composition 
of  the  combustible  mixture  and  of  compression  of  the  charge. 

The  decrease  in  the  time  occupied  by  combustion,  as  this  de- 
crease is  effected  by  the  use  of  two  simultaneous  ignition  sparks 
at  widely  separated  positions,  when  compared  with  single 
ignition,  is  more  decided  when  the  single  igniter  is  located  at 
one  side  of  the  main  volume  of  the  charge.  The  results  that 
have  been  obtained  in  a  motor  of  the  automobile  type  by  trial 
in  the  laboratories  of  the  Association  of  Automobile  Engineers 


366  ELECTRIC  IGNITION 

are  striking  examples  of  this.  The  motor  tested  had  its  inlet 
and  exhaust  valves  on  opposite  sides  of  the  cylinders.  During 
the  trials  with  single  ignition  the  spark-plug  was  located  in  one 
of  the  pockets  in  which  the  valves  are  located,  and  in  the  trials 
with  double  ignition,  a  spark-plug  was  located  in  each  of  the 
valve  pockets.  The  use  of  the  two  plugs  reduced  the  distance 
through  which  the  propagating  flame  had  to  travel  to  slightly 
more  than  half  of  its  necessary  travel  when  one  plug  was  used. 
The  electricity  was  supplied  by  a  high-tension  magneto.  The 
results  showed  not  only  a  decided  decrease  in  the  advance  of 
ignition  required  with  increased  speed  when  the  two  plugs  were 
operated,  but  also  a  very  decided  increase  of  power,  especially  at 
high  speeds.  The  two  plugs  also  made  it  possible  to  run  the  motor 
at  much  higher  speed  while  obtaining  a  large  amount  of  torque. 

207.  Advancing  and  Retarding  the  Spark  in  a  Variable-speed 
Motor.  —  On  account  of  the  extremely  wide  range  of  conditions 
under  which  an  automobile  motor  operates,  the  proper  manipu- 
lation of  the  spark  control  to  obtain  the  most  effective  results 
affords  a  complete  example  of  variation  in  the  time  of  ignition. 

When  the  motor  is  to  be  started  by  cranking,  the  spark  con- 
trol should  be  set  so  that  ignition  will  not  occur  before  dead- 
center  position  of  the  crank-shaft  if  the  ignition  is  by  battery 
current.  When  battery  current  is  used,  the  motor  can  be 
started  by  extremely  slow  cranking.  If  the  ignition  were  to 
occur  before  dead  center  while  cranking  very  slowly,  the  first 
explosion  in  the  cylinder  would  drive  the  crank-shaft  of  the 
motor  backward,  which  is  not  only  undesirable  but  dangerous 
to  the  operator.  With  magneto  ignition  the  speed  of  cranking 
must  generally  be  fast  enough  to  carry  the  crank-shaft  beyond 
dead-center  position  before  the  force  of  the  explosion  is  great 
enough  to  stop  the  rotation,  even  if  ignition  does  occur  slightly 
before  dead  center.  The  latter  statement  is  not  intended  to 
apply  to  magnetos  which  are  provided  with  a  spring  device 
for  snapping  the  rotor  of  the  magneto  over  so  as  to  produce  an 
ignition  spark  when  the  motor  is  cranked  at  slow  speed.  •  Some 
such  magnetos  are  so  constructed  as  to  make  it  impossible  to 
obtain  a  spark  before  dead  center  when  starting  the  motor  by 


VARYING  THE  TIME  OF  IGNITION  367 

external  power.  Those  without  such  a  retarding  device  must 
have  the  control  set  for  late  spark  in  the  same  manner  as  a 
battery  system. 

After  the  motor  is  started  and  while  it  is  running  light,  as 
before  the  car  is  started,  the  throttle  should  be  closed  as  far  as 
possible  without  stopping  the  motor,  and  the  spark  advanced 
only  far  enough  to  keep  the  motor  running  at  slow  speed.  This 
will  use  the  least  amount  of  fuel  and  cause  the  smallest  amount 
of  heating  of  the  motor.  When  the  car  is  to  be  started,  the 
spark  should  be  well  retarded  before  opening  the  throttle  to 
obtain  the  requisite  amount  of  torque.  While  the  car  is  running 
on  a  good  level  road,  the  throttle  should  be  closed  as  far  as 
possible  and  the  spark  advanced  as  far  as  possible  without 
reducing  the  speed  of  the  car.  If  the  motor  is  at  all  worn  so  as 
to  allow  play  in  the  working  parts,  too  much  advance  of  the 
spark  will  generally  be  indicated  by  a  characteristic  knocking  or 
pounding  in  the  motor,  as  well  as  decrease  of  power,  as  evidenced 
by  loss  of  speed  of  travel  of  the  car.  Upon  starting  up  a  hill,  in 
order  to  maintain  the  same  speed  of  travel  of  the  car,  the  spark 
must  first  be  retarded  slightly  and  the  throttle  then  opened  as 
much  as  is  found  necessary,  or  these  two  operations  may  be 
performed  simultaneously  if  it  is  possible  to  operate  both  the 
spark  and  throttle  controls  simultaneously.  The  retard  of  the 
spark  is  necessary  on  account  of  the  higher  rate  of  combustion 
that  accompanies  the  increased  amount  of  the  charge  and  the 
consequent  increased  intensity  of  compression  pressure.  The 
reverse  manipulation  of  the  spark  and  throttle  are  in  order  when 
the  car  has  reached  the  top  of  the  hill  and  again  starts  on  a 
piece  of  good  level  road.  If  the  speed  of  the  car  is  to  be  in- 
creased gradually  on  a  level  road,  then  the  throttle  can  be  opened 
gradually  without  retarding  the  spark.  The  increasing  speed  of 
the  motor  compensates  the  increasing  rate  of  combustion  due 
to  the  larger  charge  and  the  consequent  higher  compression. 

When  the  motor  is  pulling  at  slow  speed  of  rotation  on  open 
throttle  along  a  heavy  road  or  up  a  hill,  the  spark  should  be 
well  retarded,  since  otherwise  there  will  be  loss  of  power  and, 
in  a  worn  motor,  knocking  or  pounding. 


CHAPTER  XXIV. 
CARE  AND  ADJUSTMENT  OF  IGNITION  SYSTEMS. 

Introductory.  —  This  chapter  relates  only  to  good  igni- 
tion apparatus  which  is  kept  in  order  by  proper  care.  It  does 
not  deal  with  the  troubles  that  arise  on  account  of  neglect  and 
inferior  or  defective  apparatus.  The  latter  are  reserved  for  later 
discussion. 

The  ignition  apparatus  should  be  kept  clean  and  properly 
lubricated.  The  insulated  wires  should  be  kept  free  from  oil 
as  far  as  possible.  This  is  especially  important  relative  to 
wires  that  carry  high-tension  current  for  jump-spark  ignition. 
Oil  destroys  the  insulating  property  of  rubber  insulation. 

In  case  of  unsatisfactory  ignition  suspected  to  be  due  to  the 
ignition  system,  it  is  generally  advisable  to  first  make  sure  that 
the  spark-plugs  are  clean  and  in  order,  and  that  the  battery,  if 
one  is  used  while  ignition  is  unsatisfactory,  is  capable  of  deliver- 
ing the  requisite  amount  of  current.  The  examination  and 
cleaning  of  a  spark-plug,  and  the  testing  of  a  battery,  can  gener- 
ally be  readily  accomplished. 

It  should  always  be  remembered  that  there  are  other  causes 
of  unsatisfactory  ignition  than  the  ignition  system  itself.  Prom- 
inent among  these  other  causes  is  an  improperly  proportioned 
combustible  mixture.  This  fault  can  ordinarily  be  remedied  by 
adjusting  the  carbureter  when  one  is  used  for  liquid  fuel,  or  the 
proportioning  device  when  gas  is  used  as  the  fuel.  Water  in 
liquid  fuel  is  a  cause  of  a  lean  combustible  mixture,  and  leakage 
of  water  into  the  combustion  chamber  of  the  motor  may  cause 
ignition  trouble  on  account  of  the  water  collecting  on  the 
igniter. 

All  of  the  matter  given  below  does  not  relate  to  any  one 
ignition  system,  but  such  parts  as  do  relate  to  any  particular 
system  can  be  applied  to  it. 

368 


CARE  AND   ADJUSTMENT  OF  IGNITION   SYSTEMS         369 

209.  Cleaning  the  Spark-Plug.  —  It  not  infrequently  happens 
that  dirt  collects  on  the  insulation  or  between  the  spark-points 
of  the  igniter.     This  may  be  in  the  form  of  dry  carbon  or  of 
carbon   mixed   with   gummy   residue   of   lubricating   oil.     The 
gummy  deposit  generally  indicates  that  the  oil  used  to  lubricate 
the  motor  piston  is  unsuitable,  but  it  may  be  due  to  an  excess 
of  lubricating  oil  that  would  not  give  the  gummy  residue  if 
used  in  smaller  quantity.     Sometimes  a  flake  of  carbon  from 
some  part  of  the  walls  of  the  combustion  chamber  lodges  be- 
tween the  ignition  points  and  prevents  the   formation  of   an 
ignition  spark  or  arc. 

The  plug  can  be  cleaned,  after  removal  from  the  motor,  by 
the  use  of  a  stiff  bristle  brush  and  gasoline.  A  toothbrush  or 
a  small  stiff  brush  such  as  is  used  for  painting  is  suitable.  A 
piece  of  cloth  may  facilitate  the  cleaning  of  some  parts  of  the 
insulation.  It  is  not  generally  advisable  to  take  the  plug  apart 
unless  it  is  of  the  separable  type.  It  is  sometimes  difficult 
to  get  the  parts  of  an  ordinary  plug  together  again  so  as  to  be 
gas-tight,  and  there  is  danger  of  breaking  porcelain  insulation. 
The  insulation  of  a  plug  should  not  be  scraped  with  any  hard 
tool,  such  as  a  knife  or  screw-driver,  that  will  roughen  it,  since 
the  roughened  surface  would  take  on  and  retain  dirt  more 
readily  than  the  smooth  one. 

The  plug  should  not  be  screwed  very  tightly  into  the  motor 
if  it  has  a  taper  thread  (gas-pipe  thread),  if  it  is  replaced  while 
the  motor  is  hot,  for  when  the  plug  and  motor  come  to  the  same 
temperature  the  plug  will  bind  more  tightly  in  the  motor. 

210.  Adjusting    the    Width    of    Spark-Gap    in    Jump-spark 
Igniters.  —  The  width  of  the  spark-gap  in  a  battery  ignition 
system  should  ordinarily  be  about  •£%  of  an  inch,  but  a  wider 
gap  is  sometimes  used.     Magneto  makers  generally  recommend 
a  spark-gap  width,  for  magneto  current,  of  0.4  to  0.5  of  a  milli- 
meter (approximately  ^  to  •£$  of  an  inch)  for  plugs  and  mag- 
netos of  the  size  commonly  used  on  automobiles.     In  magneto 
ignition  systems  for  motors  much  larger  than  those  used  on 
automobiles,   and  in  which   the  spark-plug  and  magneto  are 
much   larger   than   those   for   automobile   use,   the   spark-gap 


370  ELECTRIC  IGNITION 

is  wider.  About  -fa  °f  an  incn  *s  suitable  for  these  large 
plugs. 

The  width  of  the  spark-gap  is  often  increased  in  a  magneto 
ignition  system  by  the  burning  away  of  the  points.  When  the 
spark-gap  becomes  widened  from  this  or  other  cause,  it  should 
be  adjusted  to  the  proper  width.  This  can  be  done  by  bend- 
ing the  wire  which  forms  one  side  of  the  spark-gap,  or  by  ad- 
justing the  insulated  spindle  or  other  part  of  the  plug,  according 
to  its  design.  It  is  convenient  to  have  a  gauge  of  the  proper 
thickness  to  which  the  adjustment  can  be  made.  A  piece  of 
wire  flattened  at  the  end,  or  a  piece  of  clockspring,  is  suitable. 
A  silver  dime  is  approximately  fa  of  an  inch  thick  after  the 
raised  edges  are  worn  off. 

If  a  bead  of  metal  has  formed  at  the  spark-gap,  or  if  the 
points  or  edges  have  become  rough  and  irregular,  it  is  advisable 
to  file  them  to  a  more  regular  shape.  The  end  of  a  wire  may 
be  filed  off  square  across  the  length  of  the  wire,  thus  leaving 
sharp  edges  from  which  a  spark  will  jump  more  readily  than 
from  a  smoothly  rounded  point. 

211.  Repairing  the  Spark-Points  of  Contact  Igniters.  —  The 
spark-points  of  contact  (low-tension)  igniters  generally  become 
pitted  and  uneven  where  they  make  contact  with  each  other. 
They  should  then  be  dressed  with  a  very  smooth-cut  file  so  as 
to  make  good  contact  with  each  other.     Care  should  also  be 
taken  to  see  that  the  points  separate  at  least  as  much  as  ^  °f 
an  inch  when   operated   to   draw  the  ignition   arc.     A  much 
wider  separation  than  this  is  customary  in  large  plugs,  and  also 
sometimes  in  small  ones.     There  is  no  objection,  so  far  as  the 
formation  of  the  arc  is  concerned,  to  a  wide  separation  of  the 
contact-points.     A  large  movement  involves  increased  mechan- 
ical wear  as  compared  with  slight  motion,  however. 

212.  Adjusting  the  Trembler.  —  The  trembler  should  be  ad- 
justed so  that  the  least  amount  of   battery  current  that  will 
give  a  spark  for  satisfactory  ignition  is  used.     The  amount  of 
battery  current  that  passes  through  the  trembler  can  be  meas- 
ured by  means  of  an  ammeter  inserted  in  the  battery  circuit. 
The  amount  of  current  required  varies  for  different  spark-coils. 


CARE  AND  ADJUSTMENT  OF  IGNITION  SYSTEMS          371 

For  the  more  usual  sizes  of  coils,  from  one-half  ampere  to  one 
and  a  half  amperes  is  required  for  operating  a  four-cylinder 
high-speed  motor  with  four  combustion  chambers.  In  the 
absence  of  information  as  to  the  amount  of  current  required  for 
any  particular  system,  it  can  be  determined  by  trial. 

If  there  is  more  than  one  trembler  and  spark-coil,  then  the 
current  passing  through  each  trembler  should  be  measured 
separately  and  the  tremblers  adjusted  so  that  all  take  the  same 
amount  of  current.  The  current  for  one  trembler  is  less  than 
that  for  all  of  them,  in  proportion  to  the  number  of  tremblers. 
The  sound  given  out  by  the  tremblers  should  be  of  the  same 
pitch  for  each  when  all  are  of  the  same  size  and  design. 

It  has  been  stated  that  some  tremblers  have  only  one  means 
of  adjusting  them,  while  others  have  two. 

In  the  absence  of  an  ammeter  for  measuring  the  current,  the 
tremblers  can  all  be  adjusted  to  the  same  pitch  of  sound  as 
nearly  as  possible.  In  general,  the  rate  of  vibration  of  the 
tremblers  should  be  somewhere  near  midway  between  the  high- 
est and  lowest  rate  that  will  give  ignition.  Ordinarily  more 
current  flows  when  the  rate  of  vibration  is  high  than  when  it 
is  low. 

213.  Lubricating  and  Cleaning  the  Timer.  —  When  the  timer 
is  of  the  sliding-contact  type,  the  rubbing  surfaces  should  be 
kept  well  lubricated.  This  can  be  done  by  a  copious  supply  of 
oil,  or  by  packing  the  timer  with  soft  grease  if  it  is  of  a  form 
that  will  retain  grease  in  the  casing.  Some  sliding-contact 
timers  are  continuously  lubricated  by  oil  pumped  to  them. 

For  a  timer  with  roller  contact,  it  is  generally  better  to  use 
oil  for  lubricating  than  grease.  The  grease  is  apt  to  prevent 
good  electric  contact  between  the  roller  and  the  stationary 
contact-pieces.  If  grease  is  used,  it  should  be  very  thin. 

A  timer  which  makes  only  pressure  contact  (after  the  manner 
of  magneto  interrupter  and  trembler  contacts),  and  is  not  in- 
tended to  be  submerged  in  oil,  should  not  have  any  oil  on  the 
contact-points  at  which  the  circuit  is  closed.  The  oil  sometimes 
prevents  effective  closing  of  the  circuit  when  the  contact-points 
are  covered  with  it. 


372  ELECTRIC  IGNITION 

A  timer  should  be  cleaned  whenever  dirt  has  collected  in  it 
to  an  appreciable  amount  The  dirt  may  be  only  small  par- 
ticles and  is  generally  mixed  with  the  oil  or  grease.  A  moder- 
ately soft  bristle  brush  and  kerosene  are  suitable  for  cleaning. 
Oil  should  be  applied  to  the  rubbing  surfaces  after  cleaning. 

214.  Care  of  the  Magneto  or  Dynamo.  —  A  magneto  or 
dynamo  whose  armature  shaft  runs  on  ball  bearings  requires 
only  a  very  few  drops  of  oil  on  each  bearing,  including  the  bear- 
ings of  the  distributer  shaft  when  there  is  such  a  shaft,  about 
once  a  month  in  ordinary  service.  Those  which  have  plain 
journal  bearings  and  are  equipped  with  oil  reservoirs  and  wicks 
for  keeping  the  bearings  continuously  lubricated  require  a  little 
more  oil  about  as  frequently.  Plain  journal  bearings  without 
oil  reservoirs  and  wicks  or  corresponding  devices  require  fre- 
quent oiling,  as  two  or  three  drops  daily  on  each  bearing  when 
in  continuous  use. 

In  some  magnetos  the  interrupter-lever  is  bushed  with  wood 
fiber  where  the  lever  rocks  on  the  pin  that  supports  it,  and  a 
piece  of  wood  fiber  is  fastened  to  the  end  of  the  lever  where  it 
strikes  the  cam  that  operates  the  lever.  The  wood  fiber  works 
on  the  metal  satisfactorily  without  lubrication  under  the  con- 
ditions existing  in  interrupters  of  magnetos.  When  there  are 
no  other  rubbing  parts  in  the  interrupter,  no  lubrication  of  the 
interrupter  is  necessary.  There  are  other  materials  that  can 
be  used  without  lubrication,  as  the  wood  fiber  is  used  in  this  case. 

If  the  interrupter  (contact-maker)  has  metallic  surfaces  that 
rub  against  each  other,  a  slight  amount  of  lubrication  is  gener- 
ally necessary.  Only  a  very  small  amount  of  oil  should  be 
used,  however,  so  that  there  will  not  be  an  excess  to  collect 
between  the  contact-points  and  interfere  with  their  operation 
by  preventing  good  electrical  contact  between  them. 

Care  should  be  taken  not  to  use  an  excess  of  oil  on  any  part 
of  a  magneto  or  dynamo.  If  too  much  oil  is  applied,  some  of 
it  may  get  on  the  winding  of  the  armature  and  injure  the  insu- 
lation. Oil  is  also  undesirable  on  the  commutator  of  a  dynamo. 

If  much  carbon  dust  or  dirt  collects  in  the  neighborhood  of  a 
carbon  brush,  the  brush  should  be  examined  to  see  whether  it 


CARE  AND  ADJUSTMENT  OF  IGNITION  SYSTEMS         373 

has  become  much  worn.  If  it  is  greatly  worn,  it  should  be  re- 
placed by  a  new  one. 

The  magneto  should  be  kept  clean,  especially  the  inter- 
rupter and  the  distributer.  Carbon  dust  and  particles  of  metal 
in  the  distributer  are  very  apt  to  cause  a  short  circuit  and  thus 
interfere  with  the  ignition.  The  same  is  true  to  a  less  extent  of 
the  interrupter.  A  soft  bristle  brush  or  cloth  may  be  used  for 
cleaning  either.  If  there  is  any  oil  present,  kerosene  or  gasoline 
will  facilitate  the  cleaning.  Do  not  scrape  the  non-metallic 
parts  with  a  steel  tool.  After  using  gasoline,  all  of  the  metal 
surfaces  with  which  it  came  in  contact  should  be  coated  with  a 
little  oil  or  kerosene,  except  the  contact-points  of  the  inter- 
rupter. The  coating  of  oil  can  be  put  on  with  a  piece  of  cloth 
or  a  small  brush.  It  is  not  necessary  to  coat  with  oil  after  using 
kerosene  for  cleaning. 

The  contact-points  of  the  interrupter  of  a  magneto  should  be 
adjusted  so  that  they  separate  from  ^  to  ^  of  an  inch  to 
break  the  circuit.  In  very  large  magnetos  the  separation  of  the 
contact-points  may  be  somewhat  greater  than  this  amount. 
The  contact-pieces  are  generally  threaded  so  that  they  can  be 
adjusted.  The  lock-nut  or  other  locking  device  should  be  tight- 
ened after  adjustment,  so  as  to  hold  the  contact-pieces  firmly 
in  place. 

The  commutator  of  a  small  dynamo  for  ignition  use  seldom 
requires  any  attention,  since  the  brushes  are  ordinarily  of  a 
material  that  is  self-lubricating.  The  self-lubricating  property 
is  generally  obtained  by  making  the  brushes  partly  of  graphite. 
In  the  dynamo  for  supplying  ignition  current  to  several  large 
engines,  the  brushes  are  not  always  of  such  material  as  lubri- 
cates well.  In  such  a  case,  the  commutator  should  be  lubricated 
by  applying  a  hard  lubricant  to  the  commutator  while  it  is 
running.  Sticks  or  "  candles  "  of  commutator  lubricant  can  be 
found  on  the  market. 

If  the  commutator  becomes  very  much  roughened,  it  can  be 
smoothed  by  holding  a  piece  of  fine-grained  sandpaper  (not 
emery  paper  or  emery  cloth)  against  it  while  it  is  running,  first 
lifting  the  brushes  from  contact  with  the  commutator.  In  case 


374  ELECTRIC  IGNITION 

of  extreme  roughness,  the  commutator  can  be  filed  smooth  with 
a  fine-cut  file.  The  brushes  should  always  be  lifted  from  the 
commutator  while  doing  this,  and  the  armature  run  at  as  slow  a 
speed  as  possible. 

Water  should  not  be  allowed  to  get  on  the  electric  generator 
unless  it  is  positively  waterproof,  as  are  some  of  those  made 
for  use  on  boats.  Water  injures  the  insulation,  and  in  the  inter- 
rupter it  interferes  with  the  breaking  of  the  circuit  if  it  gets 
between  the  contact-points. 

215.  Filing  or  Dressing  the  Contact-Points.  —  For  filing  the 
platinum  contact-points   of   the  interrupter  of  a  magneto  or 
trembler  coil,  only  a  very  smooth  (fine-cut,  dead-smooth)  file 
should  be  used.     A  convenient  method  of  holding  the  threaded 
contact-pieces  (contact-screws)  of  a  magneto  interrupter  is  to 
drill  and  tap  a  hole  through  a  flat  piece  of  metal  somewhat 
thinner  than  the  length  of  the  contact-piece,  and  screw  the  latter 
into  the  threaded  hole  so  that  its  contact-point  projects  slightly 
beyond  the  surface  of  the  holder.     The  projecting  end  can  then 
be  filed  level  with  the  surface  of  the  holder.     If  the  hole  is  per- 
pendicular (square)  with  the  surface  of  the  holder,  the  end  of 
the  contact-piece  will  then  be  square  with  its  length,  which  is 
the  proper  method  of  making  it.     If  the  screw  fits  loosely  in  the 
holder  so  that  it  turns  around  while  filing  it,  the  holder  should 
be  slotted  so  as  to  split  it  through  the  length  of  the  tapped 
hole.     The  screw  can  then  be  clamped  tightly  by  gripping  the 
holder  in  a  vise  so  as  to  press  the  sides  of  the  slot  toward  each 
other,  or  by  putting  a  binding  screw  through  the  holder  at  right 
angles  to  the  hole  for  the  contact-piece. 

The  contact-points  of  large  igniters  of  the  make-and-break 
type  can  be  filed  down  in  a  similar  manner.  A  coarser-cut  file 
can  be  used  than  for  the  small  points.  A  very  fine-cut  file  does 
not  remove  metal  rapidly.  It  is  advisable  to  finish  with  a 
smooth-cut  file. 

216.  Care  of  Batteries  in  General.  —  A  battery  should  be 
kept  clean  and  dry.     No  metallic  tools  or  appliances  should  be 
placed  where  they  can  come  into  contact  with  the  terminals, 
since  they  may  make  a  short  circuit,  thus  causing  rapid  exhaus- 


CARE  AND  ADJUSTMENT  OF  IGNITION  SYSTEMS         375 

tion  of  the  battery  and  unsatisfactory  ignition.  A  storage  bat- 
tery is  apt  to  be  permanently  injured  by  a  short  circuit  made  in 
this  manner.  A  collection  of  dirt  around  and  between  the  ter- 
minals, especially  if  moist,  is  enough  of  a  conductor  to  allow  the 
battery  to  discharge  slowly  through  it. 

If  the  pasteboard  covering  commonly  used  on  individual  dry 
cells  becomes  wet,  it  allows  leakage  of  current  through  it  when 
the  cells  of  a  battery  are  grouped  against  each  other  or  when 
they  are  in  a  metal  case  without  other  insulation  than  that  of  the 
pasteboard.  If  the  battery  must  be  used  after  the  pasteboard 
covering  of  the  cells  has  become  wet,  they  should  be  separated 
so  as  not  to  touch  each  other  and  should  not  be  allowed  to 
touch  a  metallic  part  so  as  to  make  metallic  connection  between 
their  coverings.  It  is  also  unadvisable  to  have  two  or  more  of 
them  in  contact  with  the  same  piece,  or  connected  pieces,  of 
wet  wood,  but  this  is  not  so  important  as  keeping  them  away 
from  metal.  In  case  of  necessity  of  keeping  them  in  use,  the 
cells  with  wet  covering  can  be  separated  from  each  other  by 
pieces  of  insulating  material,  such  as  glass,  porcelain,  or  rubber. 

Corrosion  of  the  terminals  of  a  storage  battery  can  be  pre- 
vented by  coating  the  terminals  with  vaseline,  paraffine,  or 
varnish  after  cleaning  them  thoroughly. 

217.  Keeping  Electric  Connections  Tight.  —  The  connections, 
or  fastenings,  between  different  parts  of  the  ignition  system 
should  be  kept  tight  so  as  to  make  good  electric  contact.  This 
is  more  important  in  low-tension  circuits  than  in  high-tension 
ones,  such  as  those  of  the  secondary  circuit  in  jump-spark 
systems. 

The  nuts  of  dry  batteries  of  the  ordinary  form  are  especially 
given  to  working  loose.  Such  a  nut  should  be  tightened  hard 
against  the  wire  which  it  holds,  but  not  hard  enough  to  break 
the  wire  or  cut  it  in  two.  It  is  not  bad  practice  to  use  pliers  for 
tightening  it.  If  the  nut  is  loose  on  the  thread  it  can  generally 
be  made  tight  by  removing  it  and  pinching  the  thread  of  the 
bolt  part  of  the  terminal  between  the  jaws  of  a  pair  of  pliers,  or  by 
striking  the  nut  with  a  hammer  so  as  to  slightly  close  the  hole. 
Or  the  nut  may  be  secured  in  place  with  a  drop  of  solder,  after 


376  ELECTRIC  IGNITION 

tightening.  These  practices  are  decidedly  not  recommended 
for  other  parts  of  the  ignition  system,  or  for  the  terminals  of 
storage  batteries.  If  the  cells  of  the  battery  are  securely  held 
in  place  so  as  not  to  shake  about,  there  is  very  much  less  lia- 
bility of  the  binding  nuts  working  loose  than  when  the  cells  can 
shake  about. 

218.  Testing  a  Primary  Battery.*  —  When  an  ammeter  is  per- 
manently connected  in  the  battery  circuit,  its  reading  while  the 
motor  is  running  is  an  indication  of  the  condition  of  the  battery, 
provided  there  are  no  unusual  causes  in  other  parts  of  the 
ignition  system  which  effect  a  decrease  in  the  amount  of  bat- 
tery current.  If  there  is  some  cause  of  decrease  of  battery  cur- 
rent exterior  to  the  battery,  then  a  voltmeter  connected  to 
the  battery  terminals  will  indicate  to  some  extent  the  condition 
of  the  battery.  If  the  voltage  of  the  battery  shows  normal  while 
the  system  is  operating  on  a  reduced  amount  of  current,  then 
the  trouble  is  outside  of  the  battery,  but  if  the  voltage  at  the 
battery  terminals  is  low  as  well  as  the  current,  then  the  battery 
is  at  fault.  The  fault  may  be  loose  connections  between  the 
cells  of  the  battery. 

If  a  primary  battery  is  not  delivering  the  requisite  amount 
of  current,  it  is  advisable  to  test  the  cells  separately  with  an 
ammeter.  This  can  be  done  without  disconnecting  the  cells 
from  each  other  when  they  are  of  the  type  with  exposed  ter- 
minals. The  test  is  made  by  applying  the  terminals  of  the  am- 
meter to  the  terminals  of  each  cell  to  be  tested,  after  the  manner 
that  has  already  been  described,  and  noting  the  amount  of 
current  as  indicated  by  the  ammeter.  The  terminals  of  both 
the  cell  and  the  ammeter  must  be  clean  so  as  to  make  good 
electric  connection  with  each  other.  If  the  terminals  are  not 
clean  or  not  pressed  together  firmly,  the  reading  of  the  ammeter 
is  apt  to  be  misleading.  If  one  of  the  cells  is  found  to  be  very 
much  exhausted,  as  indicated  by  the  small  amount  of  current 
that  it  sends  through  the  ammeter,  it  is  generally  advisable  to 
take  it  out  of  the  battery,  even  though  there  may  not  be  a  good 
one  at  hand  to  replace  it  immediately. 

*  Testing  storage  batteries  is  discussed  in  the  following  chapter. 


CARE  AND   ADJUSTMENT  OF  IGNITION  SYSTEMS         377 

Connecting  the  ammeter  to  one  of  the  cells  individually  in 
the  manner  just  described  may  stop  the  motor.  It  is  ordi- 
narily sure  to  stop  it  if  the  ammeter  is  connected  so  as  to  test 
two  or  more  cells  at  once. 

A  wet  primary  battery  (one  in  which  there  is  no  absorbent 
material  for  retaining  the  liquid  electrolyte)  can  be  tested  in 
the  same  manner  as  a  dry  primary  battery.  The  internal  re- 
sistance of  a  wet  cell  is  greater  than  that  of  a  dry  one;  there- 
fore, the  current  that  flows  through  an  ammeter  connected  to  the 
terminals  of  a  wet  primary  cell,  or  wet  primary  battery,  will  be 
less  than  that  from  a  dry  primary  cell  or  battery. 

It  is  advisable  to  always  use  the  same  ammeter  when  testing 
a  battery.  The  current  that  flows  through  an  ammeter  con- 
nected to  a  cell  or  battery  terminals  depends  to  some  extent 
upon  the  resistance  of  the  ammeter.  The  use  of  ammeters  of 
different  resistance  at  different  times  may  therefore  give  mis- 
leading information. 

On  account  of  the  varieties  of  forms  and  sizes  of  batteries  and 
the  different  resistances  of  ammeters,  it  is  not  possible  to  state 
with  any  degree  of  accuracy  how  much  current  a  battery  or  cell 
should  give  through  an  ammeter.  It  is  advisable  to  compare 
the  current  obtained  while  testing  a  used  battery  with  that  of 
a  like  battery  in  good  condition,  the  same  ammeter  being  used  in 
both  cases. 

The  more  thorough  methods  of  testing  storage  batteries  can 
be  applied  to  primary  batteries.  These  methods  are  given  in 
the  following  chapter. 

It  has  been  stated  earlier  that  an  ammeter  should  not  be 
applied  to  the  terminals  of  a  storage  battery  unless  the  am- 
meter is  especially  constructed  for  such  use.  Ordinary  ammeters 
are  not  so  constructed. 


CHAPTER  XXV. 
TESTING   OF  STORAGE  BATTERIES. 

Caution.  —  Do  not  connect  an  ammeter  alone  to  the  ter- 
minals of  a  storage  battery. 

219.   Voltage-and-current    Test    of    a    Storage    Battery.  — 

When  an  ammeter  and  a  voltmeter  are  permanently  connected 
into  the  ignition  system  so  that  the  ammeter  shows  the  amount 
of  current  that  flows  through  the  battery  circuit  while  the 
ignition  system  is  operating,  and  the  voltmeter  shows  the  cor- 
responding pressure  at  the  terminals  of  the  battery,  the  current 
and  voltage  readings  of  the  two  instruments  indicate  fairly  well 
the  condition  of  the  battery  relative  to  the  proportion  of  a 
full  charge  that  is  still  in  the  battery,  provided  the  battery  is 
in  good  order.  The  voltage  reading  during  the  discharge  should 
be  compared  with  the  voltage  when  the  battery  circuit  is  open, 
except  the  voltmeter  circuit.  The  open-circuit  voltage  of  two 
kinds  of  storage  cells  is  given  later  in  this  chapter.  These  two 
kinds  are  the  lead-plate  cell  and  the  nickel-iron  cell. 

A  portable  ammeter  can  of  course  be  inserted  in  the  battery 
circuit  temporarily  so  as  to  obtain  readings  of  the  current  de- 
livered by  the  battery  while  the  ignition  system  is  operating, 
and  a  portable  voltmeter  can  be  applied  at  the  same  time  to 
the  battery  terminals  in  order  to  measure  the  corresponding 
voltage. 

An  ammeter  can  be  connected  into  an  ignition  system  while 
it  is  operating  without  interfering  with  the  ignition.  This  can 
be  done  in  the  following  manner,  first  assuming  that  one  side  of 
the  battery  is  grounded:  Connect  one  terminal  of  the  ammeter 
to  the  grounded  side  of  the  battery  without  removing  the  ground 
connection  (ground  wire)  of  the  battery.  Connect  the  other 
side  of  the  ammeter  to  ground.  The  ammeter  and  ground 
wire  of  the  battery  are  then  in  parallel  with  each  other.  Then 

378 


TESTING  OF   STORAGE  BATTERIES  379 

remove  the  ground  wire  of  the  battery.  This  leaves  the  ground 
connection  through  the  ammeter  as  the  only  one  directly  be- 
tween the  battery  and  ground.  All  of  the  battery  current  must 
therefore  flow  through  the  ammeter,  assuming  that  the  battery 
has  no  circuits  which  are  not  grounded  leading  out  from  it.  In 
a  similar  manner,  an  ammeter  can  be  connected  into  any  part  of 
the  battery  circuit.  This  can  be  done  in  case  the  battery  is 
not  grounded.  There  must  be  no  apparatus  between  the  two 
points  to  which  the  ammeter  is  connected,  and  the  portion  of 
the  regular  circuit  between  the  connecting  points  of  the  am- 
meter must  be  of  low  electrical  resistance.  An  extreme  method 
is  to  connect  the  ammeter  to  two  near-together  points  of  a  wire 
and  then  cut  the  wire  between  the  places  to  which  the  ammeter 
is  connected.  The  wire  must  of  course  be  bare  and  clean  where 
the  ammeter  is  connected  to  it.  Before  removing  the  ammeter 
the  original  connections  must  be  made  again. 

A  voltmeter  can  be  connected  to  the  terminals  of  a  battery 
at  any  time  without  interfering  with  the  operation  of  the  ignition 
system. 

220.  Ammeter  in  Series  with  Resistance.  —  Probably  the 
most  satisfactory  method  of  testing  a  storage  battery  while  it 
is  not  delivering  current  to  operate  an  ignition  system  (or  any 
other  apparatus)  is  by  means  of  an  ammeter  in  series  with  a 
resistance.  The  resistance  should  be  of  such  a  value  as  to 
allow  the  flow  of  a  current  approximately  equal  to  that  for 
charging  the  battery  at  the  beginning  of  the  charge.  (The 
charging  rate  for  some  storage  batteries  is  given  later  in  this 
chapter.)  One  terminal  of  the  ammeter  should  be  connected  to 
one  terminal  of  the  battery,  and  one  terminal  of  the  resistance 
should  be  connected  to  the  other  terminal  of  the  battery.  The 
current  will  then  flow  through  the  ammeter  and  resistance  in 
series.  The  amount  of  current  that  flows  is  an  indication  of  the 
condition  of  the  battery  when  compared  with  the  amount  of 
current  that  flows  under  the  same  conditions  when  the  battery 
is  in  good  order  and  fully  charged.  A  voltmeter  used  in  con- 
junction with  the  ammeter  and  its  series  resistance  will  give 
additional  information. 


380  ELECTRIC  IGNITION 

The  resistance  to  be  used  in  series  with  an  ammeter  in  the 
manner  just  described  can  be  determined  approximately  for 
any  particular  battery  by  dividing  the  voltage  of  the  battery 
by  the  amount  of  current  that  is  to  flow.  This  is  expressed  by 
the  formula 

K       E 
R,-, 

in  which 

C  =  amperes  of  current; 

E  =  volts  pressure  of  battery; 

R  =  ohms  of  resistance. 

If  the  average  voltage  of  the  battery  is  6  volts  while  dis- 
charging at  the  rate  to  be  used  in  the  test,  which  will  be  taken 
as  5  amperes,  then,  substituting  in  the  formula  the  values 
E  =  6  and  C  =  5, 

R  =  —  =  1.2  ohms. 

5 

It  is  on  the  safe  side  to  first  use  a  resistance  larger  than  the 
1.2  ohms  thus  obtained,  and  then  decrease  the  resistance  to 
obtain  the  desired  amount  of  current.  After  the  resistance  is 
once  determined  in  the  latter  manner  it  should  not  be  changed, 
since  such  a  change  would  be  contrary  to  the  method  of  making 
the  test  of  the  battery,  especially  when  no  voltmeter  is  used. 

The  resistance  to  be  used  in  series  with  the  ammeter  may  be 
in  the  form  of  a  bare  wire  exposed  so  as  to  radiate  the  heat 
generated  by  the  current  passing  through  it,  of  a  rheostat,  or 
of  wire  embedded  in  enamel.  A  sufficient  number  of  low- 
resistance  incandescent  lamps,  in  parallel  with  each  other  and  the 
group  of  lamps  in  series  with  the  ammeter,  are  suitable.  The 
amount  of  current  that  will  flow  through  the  lamps  in  parallel 
with  each  other  is  approximately  proportional  to  the  number  of 
lamps  of  equal  resistance,  under  the  conditions  mentioned.  The 
wire  embedded  in  enamel  can  be  made  up  in  a  form  convenient 
for  portable  use.  Special  resistance,  or  rheostat,  wire  is  gener- 
ally used  for  such  purposes  as  the  above,  but  ordinary  iron  or 
steel  wire  will  answer  for  a  time  at  least.  The  resistance  of  an 


TESTING  OF  STORAGE   BATTERIES  381 

iron  wire  25  feet  long  and  No.  18  American  wire  gauge  is  about 
1.2  ohms.     As  the  wire  becomes  hot  its  resistance  increases. 

221.  Lamp    for    Testing.  —  An    incandescent   electric   lamp 
which  glows  at  a  voltage  the  same  as  that  of  the  storage  battery 
to  be  tested  is  a  convenient  means  of  testing  such  a  battery. 
If  the  lamp  requires  only  a  small  proportion  of  the  amount  of 
current  that  the  battery  can  deliver  at  its  maximum  safe  rate  of 
output,  then  the  lamp  can  be  connected  to  the  terminals  of  the 
battery  while  the  latter  is  delivering  current  for  ignition.     If  the 
lamp  glows  only  dimly,  it  is  an  indication  that  the  voltage  of 
the  battery  is  lower  than  it  should  be.     It  should  be  remembered 
that  a  lamp  which  glows  brilliantly  in  the  dark  will  appear  dull 
in  daylight,  and  very  dull  in  bright  sunlight. 

222.  Testing  Cells  Individually.  —  Each  cell  of  the  storage 
battery  should  be  tested  separately  when  the  battery  is  of  the 
open  type  such  that  the  terminals  of  the  cells  can  be  readily 
reached.     Each  cell  of  a  battery  should  give  the  same  readings 
when  tested  with  the  same  testing  instruments.     In  the  case  of 
portable  storage  batteries  which  are  sealed  so  as  to  prevent 
spilling  of  the  liquid,  the  terminals  of  the  individual  cells  are 
generally  so  inclosed  in  the  battery  box  that  they  cannot  be 
reached  for  testing  without  unsealing  the  cell.     This  is  not  gen- 
erally advisable  unless  the  battery  is  in  a  bad  condition  which 
cannot  be  remedied  without  unsealing  it.     The  trouble  may  be 
due  to  the  electrolyte  not  being  of  the  proper  strength,  which 
can  be  remedied  without  unsealing  the  cell. 

223.  A  voltmeter  test  of  a  storage  battery  that  is  on  open 
circuit  is  of  practically  no  value  alone  when  the  battery  is  in 
good  order,  since  the  voltage  of  the  battery  on  open  circuit  is 
practically  the  same  whether  the  battery  contains  a  large  or  a 
small  proportion  of  its  full  charge.     If  the  battery  is  in  extremely 
bad  order,  the  voltage  may  be  low. 

224.  Voltage-drop  Test.  —  Tests  which  show  when  a  rapid 
drop  of  voltage  begins  while  the  battery  is  discharging  at  a 
constant  rate  are  valuable  for  indicating  the  proportion  of  the 
charge  that  still  remains  in  the  battery.     Since  there  may  also 
be  a  rapid  drop  of  pressure  just  at  the  beginning  of  a  discharge 


382  ELECTRIC  IGNITION 

after  the  battery  has  been  fully  charged,  the  actual  voltage  must 
also  be  taken  into  consideration  in  the  absence  of  knowledge  as 
to  about  how  much  electricity  the  battery  has  given  out  since  it 
was  charged. 

225.  Lowest  Safe  Voltages  of  Storage  Batteries  While  Dis- 
charging. —  It  has  been  stated  that  when  a  storage  battery  is 
discharging,  the  drop  of  voltage  between  the  terminals  of  the 
battery  is  less  while  the  battery  is  delivering  a  small  current 
than  while  it  is  delivering  a  large  one.  The  current  which  a 
storage  battery  is  called  upon  to  furnish  an  ignition  system  is 
generally  small  in  comparison  with  that  which  the  battery  is  capa- 
ble of  furnishing  continuously  for  a  shorter  period  of  time  cover- 
ing its  complete  discharge.  The  current  supplied  to  the  ignition 
system  is  also  generally  small  in  comparison  with  the  amount  of 
current  sent  through  the  battery  while  charging  it  at  the  nor- 
mal rate.  Since  storage  batteries  especially  intended  for  ignition 
service  are  not  generally  rated  with  regard  to  the  maximum 
amount  of  current  (amperes)  they  can  deliver  efficiently  through- 
out the  entire  period  of  discharge,  and  since  the  normal  rate  of 
current  flow  while  charging  them  is  generally  given  and  should 
always  be  known,  it  is  convenient  to  refer  the  rate  of  discharge 
to  the  normal  rate  of  charging. 

While  a  lead-plate  storage  battery  is  discharging  at  a  rate 
which  is  about  one-fifth  to  one-fourth  of  the  normal  rate  of 
charging  the  battery,  the  discharge  should  not  be  continued 
after  the  voltage  (while  discharging)  has  dropped  to  1.8  volts 
for  each  cell  of  the  battery,  and  the  discharge  should  not  gener- 
ally be  continued  long  after  the  voltage  (measured  while  dis- 
charging) has  dropped  to  1.9  volts.  The  safe  minimum  voltage 
is  not  the  same,  however,  when  the  battery  is  new  as  after  it  has 
been  charged  and  discharged  several  times,  and  it  is  somewhat 
lower  when  the  electrolyte  is  weak  than  while  it  is  up  to  full 
strength  for  the  discharged  condition  of  the  battery.  The 
normal  average  voltage  of  a  lead-plate  storage  battery,  while 
discharging  at  the  rate  common  to  ignition  service,  is  2.0  volts, 
or  slightly  more,  per  cell. 

In  the  nickel-iron  storage  battery  the  voltage  should  probably 


TESTING  OF   STORAGE   BATTERIES 


383 


not  be  allowed  to  drop  below  i.i  volts  per  cell  while  the  battery 
is  discharging  at  a  rate  as  low  as  one-fourth  of  the  charging  rate 
of  the  battery.  The  minimum  allowable  voltage  may  be 
slightly  lower,  however,  if  the  electrolyte  is  below  its  normal 
strength.  The  normal  average  discharge  voltage  of  a  nickel- 
iron  storage  battery,  while  delivering  current  at  the  low  rate 
mentioned  above,  is  slightly  more  than  1.2  volts  per  cell. 

The  greatly  increased  rapidity  of  the  drop  of  voltage,  which 
begins  shortly  before  the  battery  is  discharged  as  far  as  it  should 
be,  is  the  surest  indication  of  the  nearly  complete  discharge  of 
the  battery.  After  the  rate  of  drop  becomes  rapid  the  bat- 
tery discharge  should  be  stopped.  Discharge  carried  on  after 
this  condition  has  arrived  is  very  apt  to  be  injurious  to  the 
battery. 

226.  Curve  of  Voltage  Drop  While  a  Storage  Battery  is  Dis- 
charging. —  In  Fig.  286  the  curved  line  represents  the  voltage  of 


1.50 

1.40 

1  *30 

\ 

^^^ 

1.20 
1.10 
,1.00 

{ 

'^^ 

—•—  . 

—  •  — 

••   ., 

»    » 

"     - 

S^^M 

—  —  — 

—  —  — 

"•              ~ 

*—           • 

*-       — 

-^*> 

-"  »», 

X 

\ 

)             40             80            120           160           200           240           280           320           30 
Minutes 

FIG.  286. 

Curve  Showing  Voltage  Drop  of  Nickel-iron  Storage  Battery  while  Discharging 

to  Advisable  Limit. 


a  nickel-iron  storage  battery  discharging  at  its  normal  rate 
(with  other  conditions  also  normal).  The  voltage  drops  rapidly 
during  the  first  five  minutes  or  so,  then  the  drop  becomes  more 
gradual,  and  has  a  minimum  rate  at  about  the  middle  of  the 
discharge,  then  becomes  more  rapid  again  at  the  end.  The 
battery  is  practically  discharged  when  the  voltage  has  dropped 
to  i.o  volt.  If  the  rate  of  discharge  were  slower,  the  voltage  at 
the  same  stage  of  discharge  would  be  higher. 


384  ELECTRIC  IGNITION 

227.  Testing  the  Density  of  the  Electrolyte.  —  Apparatus 
suitable  for  testing  the  density  of  the  electrolyte  for  a  storage 
cell  is  shown  in  Fig.  287.  It  consists  of  a  tubular  testing  glass 
for  holding  the  portion  of  the  electrolyte  to  be  tested,  a  syringe 
for  withdrawing  some  of  the  electrolyte  from  the  cell  and  putting 
it  into  the  testing  glass,  and  a  hydrometer  which  is  to  be  immersed 
in  the  electrolyte  for  determining  its  density.  The  stem  of  the 
hydrometer  is  graduated  so  that  a  reading  can  be  taken  at  the 
surface  of  the  liquid.  The  hydrometer  does  not  sink  so  deep 


FIG.  287. 
Hydrometer,  Testing  Glass,  and  Syringe. 

into  a  liquid  of  high  density,  or  high  specific  gravity  (a  heavy 
liquid),  as  into  one  of  lower  density.  A  strong  electrolyte  has 
greater  density  than  a  weak  one. 

The  stem  of  the  hydrometer  may  be  graduated  to  read  in 
density  (specific  gravity),  but  of  those  found  on  the  market 
some  are  graduated  to  a  different  scale.  Of  these  other  scales 
the  Baume  is  found  most  often.  The  following  table  gives  the 
densities  corresponding  to  a  portion  of  the  graduations  of  a 
Baume  hydrometer  sufficient  for  testing  the  electrolytes  most 
commonly  used  in  storage  batteries. 


TESTING  OF  STORAGE  BATTERIES  385 

DENSITY  COMPARED  WITH  BAUME  HYDROMETER. 


Baum6 
Degrees. 

Density. 

Baume 
Degrees. 

Density. 

Baume 
Degrees. 

Density. 

2O 

1.152 

25 

I.I97 

30 

1.246 

21 

1.  160 

26 

I.  206 

31 

1  .256 

22 

1.  169 

27 

1.216 

32 

I.  267 

23 

1.178 

28 

i.  226 

33 

1.277 

24 

1.188 

29 

i  .  236 

34 

1.288 

A  more  compact  device  for  testing  specific  gravity  is  shown  in 
Fig.  288.     The  hydrometer  is  inclosed  in  the  glass  body  of  the 


FIG.  288. 
Combined  Hydrometer  and  Syringe. 

syringe,  so  that,  by  drawing  a  sufficient  amount  of  the  liquid 
into  the  syringe  to  make  the  hydrometer  float,  a  reading  can  be 
obtained. 

A  thermometer  is  a  necessary  accessory  to  the  hydrometer 
testing  set  if  the  electrolyte  is  sometimes  warm  and  sometimes 
cool  when  it  is  tested.  The  electrolyte  has  less  density  when 
warm  than  when  cool,  within  the  range  of  temperature  that  is 
allowable  during  the  operation  of  the  battery.  Within  this 
range  the  density  decreases  about  .001  for  3  Fahrenheit  degrees 
rise  of  temperature.  Accordingly,  if  the  density  is  1.280  at  80° 
Fahrenheit,  a  rise  of  temperature  of  30  degrees  (to  110°  Fahren- 
heit) will  cause  a  density  drop  of  -^°-  X  .001  =  .01,  thus  making 
the  density  1.270  at  the  higher  temperature. 

Ordinarily  the  temperature  of  the  electrolyte  is  supposed  to 
be  at  about  80°  Fahrenheit  when  speaking  of  its  density. 

The  electrolyte  should  be  returned  to  the  same  cell  from 


386  ELECTRIC  IGNITION 

which  it  was  withdrawn,  in  order  not  to  lower  the  level  of  the 
liquid  in  the  cell. 

The  density  of  the  sulphuric-acid  electrolyte  for  one  prominent 
make  of  storage  cells  of  the  lead-plate  type  is  recommended  by 
the  manufacturer  to  be  between  1.275  and  1-300  while  the  cell 
is  fully  charged.  The  lower  density  just  given  drops  to  about 
1.20  by  the  time  the  cell  is  fully  discharged,  and  retains  this 
lower  value  during  the  time  the  cell  remains  discharged.  It  is 
not  injurious  to  use  a  slightly  lower  density  down  to  1.25  in  the 
fully  charged  cell  for  a  while.  The  density  in  the  discharged 
cell  is  correspondingly  lower  with  this  weaker  electrolyte. 

The  potassium-hydrate  electrolyte  for  the  nickel-iron  Edison 
storage  battery  is  1.200,  as  recommended  by  the  manufacturers 
of  the  battery.  The  specific  gravity  does  not  vary  appreciably 
during  the  charging  and  discharging  of  the  battery  under  normal 
conditions.  It  is  stated  by  the  manufacturer  that  the  efficiency 
and  capacity  of  the  battery  is  not  affected  materially  by  allow- 
ing the  density  of  the  electrolyte  to  become  as  low  as  1.16,  but 
that  if  it  gets  below  this  the  output  of  the  battery  will  be  tem- 
porarily affected. 


CHAPTER  XXVI. 

CHARGING  AND   CARE   OF   STORAGE  BATTERIES. 

228.  Precautions.  —  When   charging   a   storage   battery  the 
following  three  important  items,  among  others,  should  be  re- 
membered : 

First  Item.  —  Only  a  direct  current  can  be  used.  An  alter- 
nating current  will  not  charge  the  battery  and  is  apt  to  injure 
it.  But  an  alternating  current  can  be  transformed  into  a  direct 
current  that  is  suitable  to  charge  the  battery. 

Second  Item.  —  The  positive  (+)  terminal  of  the  charging 
source  must  be  connected  to  the  positive  (+)  terminal  of  the 
battery,  and  the  negative  (  — )  terminal  of  the  charging  source  to 
the  negative  ( — )  terminal  of  the  battery,  but  suitable  resistance 
must  generally  be  placed  in  the  circuit  to  regulate  the  current 
to  the  proper  amount.  Methods  of  determining  which  is  the 
positive  side  of  a  circuit  and  which  the  negative,  have  been 
given  earlier. 

Third  Item.  —  An  excessive  current  must  not  be  allowed  to 
pass  through  the  battery.  It  is  injurious  and  will  overheat  the 
battery  if  continued  long. 

229.  Connections  for  charging  a  storage  battery  from  a  light- 
ing circuit   of   fixed  voltage  are  shown  in   Fig.    289.     If   the 
charging  is  to  be  done  at  the  rate  of  6  amperes,  then  12  lamps 
of  1 6  candle-power  each,  or  6  lamps  of  32  candle-power  each,  of 
the  ordinary  carbon-filament  type,  can  be  used  as  the  resistance. 
The  lamps  are  used  in  parallel  with  each  other.    If  some  other 
kind  of  incandescent  lamp  of  higher  efficiency  (requiring  less 
current  per  candle-power)  is  used  for  the  resistance,  then  more 
lamps  will  be  required.     Thus,  if  each  lamp  takes  one- third  of 
an  ampere,  18  lamps  will  be  required. 

If  one  side  of  the  circuit  from  which  current  is  to  be  taken 
is  grounded,  as  in  the  case  of  most  electric  railway  circuits,  then 
the  corresponding  side  of  the  battery  should  be  connected  to 

387 


388 


ELECTRIC  IGNITION 


ground  without  any  resistance  of  substantial  value  between  the 
battery  and  ground.     If  the  main  resistance  is  placed  between 


FIG.  289. 

Lamp  Resistance  and  Switch  Connected  to  a  Storage  Battery  for  Charging  the 

Battery. 


FIG.  290. 
Rheostat  and  Switch  Connected  to  a  Storage  Battery  for  Charging  it. 

the  battery  and  ground,  there  is  probability  of  the  operator  re- 
ceiving a  dangerous  shock. 
A  fuse-block  with  two  fuses  is  shown  just  above  the  switch 


CHARGING  AND  CARE  OF  STORAGE  BATTERIES          389 

at  the  right-hand  side  of  the  illustration.  The  fuses  are  of  the 
type  commonly  used  in  lighting  circuits. 

In  Fig.  290,  a  rheostat  is  used  for  the  resistance  in  the  charg- 
ing circuit;  also  an  ammeter  for  measuring  the  charging  current. 
The  rheostat  is  used  to  vary  the  amount  of  resistance  in  the 
circuit,  so  as  to  regulate  the  current  to  the  desired  amount  at 
any  time. 

The  resistance  required  in  the  charging  circuit  can  be  deter- 
mined by  the  formula 


in  which 

C  =  amperes  of  charging  current; 
E  =  voltage  of  the  charging  circuit; 
e  =  voltage  of  the  storage  battery; 
R  =  ohms  of  resistance. 

If  the  voltage  of  the  charging  circuit  (line  voltage)  is  no 
volts,  and  that  of  the  battery  is  6  volts,  then,  if  the  charging 
is  to  be  done  at  the  rate  of  4  amperes, 

-n      no  —  6       104 

R  —  -         -  =  — -  =  26  ohms. 

4  4 

It  is  advisable  to  make  the  resistance  somewhat  larger  than 
the  value  determined  in  this  manner,  to  allow  for  variation  in 
the  line  voltage  and  to  be  able  to  get  a  smaller  current  if  desired. 

230.  Connections  for  charging  two  batteries  at  the  same 
time  are  shown  in  Fig.  291.  As  illustrated,  the  two  batteries 
are  supposed  to  be  in  one  box.  Each  battery  consists  of  three 
cells  connected  in  series.  The  two  batteries  are  not  electrically 
connected  together. 

The  positive  terminal  of  the  main  battery  is  at  A ;  its  negative 
terminal  is  at  B.  The  positive  terminal  of  the  reserve  battery 
is  at  P,  and  its  negative  terminal  is  at  N.  C  is  the  charging 
circuit;  D  is  a  double-pole  double-throw  switch;  £  is  a  single- 
pole  single-throw  switch  for  the  reserve  battery.  At  M  are  six 
lamps  for  resistance  in  the  main  battery  circuit,  and  at  R  is  one 
lamp  for  resistance  in  the  reserve  battery  circuit. 


390 


ELECTRIC  IGNITION 


The  purpose  of  having  a  large  and  a  small  battery  in  the 
same  box,  as  just  shown,  is  that  the  large  one  can  be  used  till  it  is 

•9 


M 


in  Batte 


A 


E     R 

'^ 


FIG.  291. 
Connections  for  Charging  Two  Storage  Batteries  at  the  Same  Time. 

fully  discharged,  and  then  the  small  one  can  be  used  to  supply 
current  for  a  short  time  till  recharging  can  be  done. 

231.  The  rate  of  charging  a  storage  battery  should  always  be 
given  in  instructions  accompanying  it.     In  the  absence  of  such 
information  the  matter  given  in  the  following  two  sections  will 
serve  as  a  guide.     On  account  of  the  differences  in  the  form  and 
construction  of  batteries,  it  is  not  possible  to  make  accurate 
statements  to  cover  the  different  varieties. 

232.  Charging  and  Care  of  Lead-plate  Storage  Batteries.  - 
The  following  is  extracted  from  the  instruction  book  for  "  Exide  " 
batteries  of  the  portable  type  sealed  in  a  case  and  intended  for 
ignition  use : 

"  When  a  battery  is  received,  remove  and  discard  the  soft 
rubber  caps  from  the  vent-plugs  and  see  if  the  electrolyte  (the 
liquid  in  the  jars)  is  at  the  proper  height  (about  one-fourth  inch, 
but  not  more)  above  the  top  of  the  plates;  if  it  is  lower,  add 
electrolyte  of  1.300  specific  gravity. 

"  The  battery  should  not  be  discharged  below  the  point  of 
exhaustion,  i.e.,  1.80  volts  per  cell  when  the  current  is  flowing; 
thus,  with  a  3-cell  battery,  the  voltage  should  not  be  allowed  to 
fall  below  5.40  volts.  Nor  should  it  be  allowed  to  stand  com- 


CHARGING  AND   CARE  OF   STORAGE   BATTERIES          391 

pletely  discharged.  Never  attempt  to  test  the  condition  of  the 
cells  with  an  ammeter,  as  is  the  practice  with  dry  cells.* 

"  Immediate  recharging  is  necessary  when  the  discharge  limit 
is  reached.  If  it  is  not  possible  to  fully  charge  at  once,  then  a 
partial  charge  must  be  given,  and  the  charge  completed  as  soon 
as  possible  and  before  again  discharging. 

"  Always  charge  the  battery  at  least  once  every  two  months, 
whether  used  or  not;  this  rule  also  applies  if  the  battery  is  to  be 
out  of  service  for  any  length  of  time,  say  for  the  winter  months. 

">When  the  battery  is  to  be  charged,  unscrew  the  vent-plugs, 
observe  the  height  of  the  electrolyte,  and  add  pure  fresh  water 
if  low,  bringing  the  height  up  to  one-fourth  inch  above  the 
plates,  but  not  higher. 

"  Charge  at  the  rate  given  on  the  name-plate  on  the  case, 
until  there  is  no  further  rise  in  the  voltage  of  the  battery  and 
each  cell  has  been  gassing  or  bubbling  freely  for  at  least  five 
hours,  and  there  is  also  no  further  rise  in  the  specific  gravity  of 
the  electrolyte  over  the  same  period.  The  voltage  at  the  end 
of  the  charge  may  be  between  2.40  and  2.70  volts  per  cell,  de- 
pending on  the  temperature  and  age;  the  higher  voltages  are 
obtained  on  new  batteries  with  the  temperature  low;  on  old 
batteries  at  high  temperatures  the  low  voltages  are  obtained. 
It,  therefore,  must  be  understood  that,  in  determining  the  com- 
pletion of  the  charge  a  fixed  or  definite  voltage  is  not  to  be  con- 
sidered, but  rather  a  maximum  voltage,  as  indicated  by  there 
being  no  further  rise  in  the  voltage  over  a  period  of  five  hours. 
It  is  of  the  utmost  importance  that  the  charge  be  complete. 

"  The  temperature  of  the  electrolyte  during  charge  should 
not  be  allowed  to  get  above  100°  Fahrenheit,  unless  this  cannot 
be  prevented,  due  to  high  temperature  of  the  atmosphere.  If 
it  tends  to  do  so,  either  reduce  the  charging  rate  or  discontinue 
charging  until  the  temperature  has  fallen.  Low  temperatures 
are  in  no  way  injurious,  but  they  have  the  effect  of  temporarily 
reducing  its  discharge  capacity;  a  return  to  normal  temperature 
restores  the  capacity. 

*  AUTHOR'S  NOTE.  An  ammeter  can  be  used  in  series  with  a  suitable  re- 
sistance, however,  as  described  in  the  chapter  on  "  Testing  of  Storage  Batteries." 


392  ELECTRIC  IGNITION 

"  After  charging,  replace  vent-plugs  and  wipe  off  top  and 
sides  of  case. 

"  Great  care  should  be  taken  not  to  bring  a  naked  flame  near 
the  openings  in  the  top  of  the  battery  during  or  immediately 
following  a  charge. 

"  The  proper  specific  gravity  of  the  electrolyte  at  the  end  of 
the  charge  is  1.300  *  *  *  ,  but  a  variation  of  from  1.275  to 
1.300  is  allowable.  Do  not  adjust  the  specific  gravity  except 
when  a  battery  is  fully  charged;  after  adjusting,  charge  for  an 
hour,  in  order  to  thoroughly  mix  the  liquid  just  added  with  the 
electrolyte.  Do  not  add  electrolyte  until  it  is  determined  that 
the  specific  gravity  cannot  be  brought  up  to  the  proper  point  by 
charging.  To  add  water  or  electrolyte,  use  a  rubber  syringe 
(see  Figs.  287  and  288).  Addition  of  electrolyte  is  but  seldom 
necessary. 

"  The  electrolyte  can  be  made  by  mixing  especially  pure 
sulphuric  acid  (1.840  specific  gravity)  and  distilled  water  in 
proportion  of  two  parts  of  acid  to  five  parts  of  water,  by  vol- 
ume. The  acid  must  always  be  poured  into  the  water,  and  not 
the  water  into  the  acid.  A  glass,  earthenware,  or  other  acid- 
proof  vessel,  thoroughly  cleaned,  should  be  used,  and  the  elec- 
trolyte allowed  to  cool  before  using. 

"  The  height  of  the  electrolyte  in  each  cell  should  be  observed, 
not  only  at  the  time  of  charging,  but  frequently  between 
charges,  and  if  it  is  low,  either  because  of  evaporation  or  spill- 
ing, it  should  be  brought  to  the  proper  height  (one-fourth  inch 
above  the  top  of  the  plates)  by  the  addition  of  pure  water.  If 
a  considerable  amount  of  the  electrolyte  has  been  spilled  out  of 
the  cells,  then  the  battery  should  be  given  a  special  charge  as 
soon  as  the  water  has  been  added,  and  the  specific  gravity  ad- 
justed to  the  proper  point  by  adding  some  new  electrolyte  as 
soon  as  the  charge  is  completed. 

"  The  sediment,  which  gradually  accumulates  in  the  bottom 
of  the  jars,  should  be  removed  before  it  reaches  the  bottom  of 
the  plates,  as,  if  it  does,  it  is  very  harmful  to  them.  The  need 
for  cleaning  is  indicated  by  lack  of  capacity,  excessive  evapora- 
tion of  the  electrolyte,  and  excessive  heating  when  charging. 


CHARGING  AND   CARE  OF   STORAGE  BATTERIES          393 

When  a  battery  requires  removal  of  the  sediment,  better  re- 
sults follow  if  the  work  is  done  at  a  place  where  they  are  ac- 
customed to  it. 

"  Keep  the  holes  in  the  vent-plugs  clear. 

"  Keep  all  connections  tight  and  clean." 

The  charging  rate  for  "Exide  "  batteries,  of  which  other  items 
are  tabulated  on  page  109,  is  as  follows: 

Ampere-hour  capacity  at  service  rate,      40    60     80     100 
Charging  rate  in  amperes     ....        4      6       8       10 

It  may  be  seen  that  the  charging  rate  can  be  obtained  by 
dividing  the  ampere-hour  capacity  by  10. 

In  order  to  maintain  a  constant  charging  rate,  the  resistance 
in  the  charging  circuit  must  be  reduced  as  charging  progresses, 
if  the  voltage  of  the  source  of  electric  supply  remains  constant. 
It  is  not  objectionable,  and  often  advisable,  to  charge  at  a  slower 
rate  toward  the  completion  of  the  charge  than  during  the  early 
portion. 

233.  Removing  Sediment  from  Lead-plate  Cells.  —  In  order 
to  remove  the  sediment  which  collects  at  the  bottom  of  a  cell, 
the  plates  and  electrolyte  must  be  taken  out  of  the  containing 
vessel,  which  is  usually  called  the  "  jar."  It  may  be  necessary 
to  cut  some  of  the  lead  connectors  between  the  plates  or  be- 
tween cells. 

The  cell  should  first  be  fully  charged  so  that  the  voltage 
remains  constant  for  an  hour  or  so  during  the  latter  part  of 
charging. 

As  soon  as  the  plates  are  removed  from  the  jar,  they  should 
be  stood  on  edge,  with  one  of  the  side  edges  at  the  bottom  and 
the  other  side  edge  at  the  top,  and  the  separators  withdrawn 
from  between  the  plates.  The  removal  of  the  separators  is  facili- 
tated by  spreading  the  plates  apart  slightly.  Then  without 
delay  wash  the  plates  with  a  gentle  stream  of  water,  as  from  a 
hose  without  a  nozzle.  Such  of  the  separators  as  are  in  a  con- 
dition to  be  used  again  after  cleaning,  should  be  washed  clean. 
If  the  electrolyte  is  to  be  used  again,  it  can  be  put  into  another 
jar,  as  by  siphoning  it  out  or  pouring  carefully  so  as  not  to  stir 


394  ELECTRIC  IGNITION 

up  the  sediment.  As  soon  as  the  jar  is  cleaned,  the  plates  can 
be  put  back  in  place,  and  the  cut  lead  connectors  "  burned  " 
(fused)  together  again.  The  burning  process  involves  skill  and 
practice,  and  will  not  be  described  here.  The  electrolyte  should 
be  put  in  the  jar  so  as  to  cover  the  plates  again  as  soon  as  they 
are  in  place,  for  the  plates  should  not  be  allowed  to  become  dry. 
If  new  wooden  separators  are  put  in  the  cell,  the  electrolyte 
should  be  made  about  3  per  cent  higher  in  specific  gravity  than 
it  was  at  the  time  of  taking  the  cell  apart.  This  is  to  allow  for 
the  diluting  effect  of  the  water  contained  in  wet  wooden  plates. 

234.  Taking  a  Lead-plate  Cell  out  of  Commission.  —  If  the 
cell  is  not  to  be  used  for  several  months,  and  it  is  not  con- 
venient to  charge  it  at  intervals  while  not  in  use,  then,  after 
being  fully  charged  so  that  the  voltage  remains  constant  for  an 
hour  or  so,  it  should  be  taken  apart,  washed,  and  the  plates 
dried.     The  taking  apart  and  washing  can  be  done  as  just  de- 
scribed.    As  soon  as  the  positive  plates  become  dry,  they  are 
ready  for  storage. 

But  if  the  negative  plates  become  so  hot  as  to  steam  while  dry- 
ing, they  should  be  washed  again,  or  wet  with  water,  and  allowed 
to  dry  again.  They  are  then  ready  for  storage. 

If  the  cell  has  wooden  separators  between  the  plates,  and  they 
are  thought  worth  keeping,  they  should  be  immediately  put  in 
water  or  electrolyte  of  low  specific  gravity,  and  left  there  during 
storage. 

235.  Charging  and  Care  of  Nickel-iron  Storage  Batteries. — 
The  normal  charging  rate  for  an  Edison  nickel-iron  battery  can 
be  obtained  by  dividing  the  rated  ampere-hour  capacity  by  5. 
The  normal  length  of  time  for  charging  is  7  hours,  but  continuing 
the  charge  3  hours  longer  will  increase  the  output  capacity  of 
the  battery  about  30  per  cent.     The  charging  current  can  be 
continued  at  its  normal  rate  till  the  end  of  the  charge  if  the 
temperature  of  the  cell  does  not  rise  above  ioo6  Fahrenheit. 
If  the  temperature  tends  to  rise  above  this  point,  the  charg- 
ing rate  should  be   decreased   or  the  cell  kept  cool  by  some 
artificial  means,  as  blowing  a  current  of  air  against  it  with 
a  fan. 


CHARGING  AND  CARE   OF  STORAGE   BATTERIES 


395 


The  voltage  rises  rapidly  at  the  beginning  of  the  charge, 
sometimes  to  a  value  within  an  hour  or  two  that  apparently 
indicates  that  the  battery  is  charged;  but  the  voltage  then 
drops  somewhat  below  this  amount  and  gradually  rises  again  to 
a  maximum  value,  which  remains  constant  at  the  end  of  the 
charge.  This  maximum  value  generally  lies  between  1.80  and 
1.85  volts  per  cell.  Charging  should  be  continued  for  30  or  40 


^---^ 

-4- 

l.oU 

i 

S 

»•••  -^ 

—  ^ 

i^—  —  1 

^^—  ^ 

fc^— 

—  ^ 

••      • 

r—  —  ^ 

fa.        ^ 

==! 

M—  —  ' 

K-—  ^ 

p-*  -" 

_ 

1.504 
1  40 

/ 

Minutes 
FIG.  292. 
Curve  Showing  Rise  of  Voltage  while  Charging  a  Nickel-iron  Storage  Battery 


minutes  after  the  voltage  becomes  constant  and  is  as  high  as 
i. 80  volts. 

Fig.  292  shows  the  curve  of  voltage  variation  of  a  nickel-iron 
cell  while  it  is  being  charged. 

Higher  rates  of  charging  can  be  used  for  a  short  time,  —  as  high 
as  double  the  normal  rate  for  an  hour,  —  but  the  temperature 
should  not  be  allowed  to  exceed  100°  Fahrenheit. 

A  lower  rate  of  charging  can  be  used,  as  when  the  charging 
source  will  not  supply  the  normal  amount  of  current,  but  this 
lower  rate  should  not  be  less  than  two-thirds  of  the  normal  rate. 
Very  low  rates  of  charging  are  injurious. 

When  a  new  nickel-iron  battery  is  first  assembled  and  put 
into  use,  it  should  be  charged  at  the  normal  rate  for  about  15 
hours.  The  same  applies  to  putting  a  battery  into  use  again 
after  it  has  been  out  of  commission. 

There  should  always  be  enough  electrolyte  to  keep  the  tops 
of  the  plates  covered.  Overcharging  causes  loss  of  water  from 
the  electrolyte  by  decomposing  the  water.  This  loss  of  water 
should  be  replaced  by  pure  distilled  water  which  is  newly  dis- 


396  ELECTRIC  IGNITION 

tilled,  or  has  been  kept  in  a  tightly  closed  vessel  to  prevent 
carbonation  by  contact  with  the  atmosphere. 

The  specific  gravity  of  the  electrolyte  does  not  change  during 
charging  and  discharging,  except  possibly  on  account  of  loss  of 
water  as  just  stated.  Its  normal  specific  gravity  is  1.200. 
Density  tests  should  be  made  at  the  end  of  a  charge;  the  liquid 
is  then  thoroughly  mixed. 

Before  putting  in  new  electrolyte  it  is  better  to  throw  away 
all  of  the  old. 

Cleaning  the  cell  is  limited  to  the  outside.  The  containing 
vessel  (can)  is  so  constructed  that  it  cannot  be  opened  to  re- 
move the  plates  without  injuring  it. 

236.  Taking  a  Nickel-iron  Battery  out  of  Commission.  —  It 
is  not  necessary  to  charge  the  battery  when  it  is  left  idle. 

"  A  battery  can  be  put  out  of  commission  indefinitely  if  care 
is  taken  to  see  that  the  outside  of  the  retaining  cans  is  left  clean 
and  dry,  and  that  the  cells  are  in  a  discharged  condition.  It 
should  be  stored  in  a  dry  place,  and  will  require  no  attention 
other  than  an  inspection  once  in  two  or  three  months  to  make 
sure  the  solution  is  kept  at  its  proper  height/' 


CHAPTER  XXVII. 

TIMING  THE  IGNITION. 

237.  General  Features.  —  In  the  more  general  cases  the  re- 
quirements of  the  ignition  system  relative  to  the  time  of  ignition 
are  that  it  shall  cause  ignition  as  early  as  desired  during  the 
compression  stroke  of  the  motor  while  the  motor  is  running,  and 
that,  while  the  motor  is  being  started,  it  shall  not  cause  ignition 
until  after  the  piston  of  the  motor  has  started  on  its  impulse,  or 
combustion,  stroke. 

The  following  statements  regarding  the  setting  of  the  timer, 
the  contact  maker,  or  the  magneto  rotor,  are  intended  to  point 
out  general  methods  of  meeting  these  requirements.  In  view  of 
the  numerous  kinds  of  ignition  systems  and  the  varied  nature 
of  the  mechanical  part  of  their  operation,  the  method  which 
best  meets  the  requirements  of  each  specific  case  should  be 
selected  and,  if  necessary,  suitably  modified. 

The  instructions  of  the  manufacturer  of  the  apparatus  should 
be  followed  in  preference  to  the  general  instructions  given  herein. 

When  the  connections  to  the  ignition  control  are  apt  to  have 
considerable  lost  motion  on  account  of  wear  or  loose  fitting,  an 
allowance  should  be  made  for  this  lost  motion. 

In  a  system  which  will  give  an  ignition  spark  or  arc,  however 
slow  the  rotation  of  the  crank-shaft  of  the  motor,  such  as  a 
system  operating  on  current  from  some  source  which  will  supply 
current  whether  the  motor  is  rotating  or  not,  a  timer  operating 
in  conjunction  with  a  trembler  spark-coil  or  with  a  magnetically 
operated  igniter  must  not  close  the  circuit,  when  the  spark  con- 
trol is  in  position  for  latest  ignition,  until  after  the  crank-shaft 
of  the  motor  has  passed  its  dead-center  position;  and  an  inter- 
rupter must  not  break  the  circuit  until  after  the  crank-shaft 
has  passed  its  dead-center  position  when  operating  on  current 
similarly  supplied. 

397 


ELECTRIC  IGNITION 

Precaution  should  be  taken  to  prevent  an  impulse  of  the 
motor  while  timing  the  ignition.  The  removal  of  the  spark-plug 
or  disconnecting  the  wires  from  it,  in  a  high-tension  system,  will 
prevent  ignition.  In  a  low-tension  system,  the  opening  of  a 
petcock  so  as  to  connect  the  combustion  chamber  with  the 
atmosphere  will  prevent  an  impulse  of  the  motor.  In  the 
absence  of  the  petcock,  some  part  may  be  removed  to  make  an 
opening  into  the  combustion  chamber.  If  there  is  no  com- 
bustible mixture  in  the  motor,  there  can  of  course  be  no  ignition 
without  these  precautions.  But  certainty  in  this  respect  is  apt 
to  be  like  that  regarding  a  gun  which  is  not  loaded. 

238.  Timing,  or  Setting,  a  Timer.  —  This  can  be  done  by 
either  of  the  following  two  methods,  according  to  which  is  the 
more  convenient: 

First  Method.  —  Rotate  the  crank-shaft  of  the  motor  some- 
what past  one  of  its  dead-center  positions,  say  10  to  20  degrees 
of  angle  past,  so  that  one  of  the  pistons  has  moved  a  slight  dis- 
tance on  its  impulse,  or  combustion,  stroke.  Leave  the  crank- 
shaft in  this  position. 

In  a  jump-spark  system,  disconnect  the  wire  from  the  spark- 
plug for  the  cylinder  whose  piston  is  on  the  impulse  stroke,  and 
place  the  disconnected  end  of  the  wire  within  an  eighth-inch 
from  the  metal  of  the  motor;  or  remove  the  spark-plug  from  its 
position  and  place  it  so  that  its  outer  bushing  makes  contact 
with  the  metal  of  the  motor,  but  its  insulated  spindle  and  the 
end  of  the  connection  to  it  do  not  make  electric  connection  with 
the  metal  of  the  motor. 

Loosen  the  timer  rotor  from  the  part  (shaft)  that  drives  it, 
so  that  the  timer  rotor  can  be  revolved  without  rotating  its 
driver  with  it.  Move  the  spark  control  to  its  position  for 
latest  spark.  Moving  the  part  of  the  timer  to  which  the  con- 
trol is  connected  around  in  the  direction  of  rotation  of  the  timer 
rotor  retards  ignition. 

Revolve  the  timer  rotor  slowly  in  the  direction  that  it  rotates 
while  operating,  until  it  closes  its  circuit,  as  indicated  by  a 
spark  at  the  plug  mentioned,  or  by  movement  of  the  magnetic 
igniter  corresponding  to  the  cylinder  whose  piston  is  on  the  com- 


TIMING  THE  IGNITION  399 

bustion  stroke,  as  the  case  may  be.  Fasten  the  timer  rotor  to 
its  driver  permanently  in  the  position  thus  determined. 

Judgment  must  be  used  in  selecting  the  value  of  the  angle  of 
the  crank-shaft  past  dead  center  for  timing  in  this  manner. 
If  there  is  probability  of  much  wear  in  the  control  connections, 
the  angle  should  generally  be  made  more  than  10  degrees  when 
the  motor  is  to  be  started  from  rest  or  from  extremely  slow 
speed  of  rotation,  by  the  impulse  of  an  ignited  charge  in  its 
cylinder. 

The  movement  of  the  spark  control  must  be  sufficient  to  give 
the  greatest  advance  desired. 

If  the  timer  rotor  is  mounted  on  a  shaft  separate  from  the 
cam-shaft  or  crank-shaft,  and  which  is  only  for  driving  the  timer 
rotor,  then  the  desired  setting  of  the  rotor  can  be  obtained  ap- 
proximately by  taking  the  driving  gears  out  of  mesh  with  each 
other  and  then  putting  them  into  mesh  again  in  the  desired 
position.  The  accuracy  of  adjustment  by  this  method  is  limited 
to  half  of  the  angular  movement  of  the  timer  rotor  due  to  mov- 
ing the  gear  on  its  shaft  one  tooth  forward  or  backward  relative 
to  the  gear  which  meshes  with  it.  This  method  can  be  used, 
under  the  restrictions  mentioned,  when  the  timer  rotor  and  its 
gear  are  keyed  or  otherwise  fastened  permanently  in  position  on 
the  shaft.  It  is  immaterial  whether  the  timer  shaft  also  drives 
a  pump  for  cooling  water  or  lubricating  oil. 

Second  Method.  —  Bring  the  crank-shaft  to  one  of  its  dead- 
center  positions  so  that  one  of  the  pistons  is  at  the  end  of  its 
compression  stroke  and  ready  to  begin  its  impulse  stroke. 

Loosen  the  timer  rotor  from  the  shaft  or  other  part  that 
drives  it,  so  that  the  timer  rotor  can  be  revolved  without  rotat- 
ing its  driver  with  it. 

Move  the  spark  control  to  the  position  thought  to  be  correct 
for  ignition  at  dead  center  while  the  motor  crank-shaft  is  rotated 
at  very  slow  speed,  as  when  starting  the  motor.  This  position, 
for  a  high-speed  motor,  would  generally  be  not  more  in  advance 
of  the  position  for  latest  ignition  than  one-fifth  of  the  entire 
movement  of  the  control.  It  may  be  more  in  advance  for  a 
slow-speed  motor. 


400 


ELECTRIC  IGNITION 


The  remainder  of  the  timing  is  the  same  as  that  in  the  second, 
third,  and  fourth  paragraphs  of  the  first  method,  just  given. 

239.  Timing  a  Rotary  Magneto  of  the  Interrupter  Type.  —  It 
should  always  first  be  made  certain  that  the  magneto  itself  is  so 
adjusted  that  its  interrupter  breaks  the  primary  circuit  in  accord 
with  the  proper  corresponding  position  of  the  rotating  armature 
or  inductor.  The  ordinary  method  of  determining  this  in  a 
magneto  with  rotating  armature  is  by  measuring  the  distance 
A  in  Fig.  293  between  the  lip  of  the  pole-piece  and  the  edge  of 
the  armature  core,  after  the  core  has  passed  beyond  the  position 
in  which  its  crowned  parts  bridge  the  space  between  the  pole- 


FIG.  293. 

Position  of  Armature  for  Timing  a  Magneto  by  the  Advanced  Spark-control 

Method. 

pieces.  The  arrows  indicate  the  direction  of  rotation  of  the 
armature.  The  distance  A  is  as  small  as  one-sixteenth  inch  for 
some  magnetos,  and  as  large  as  one-fourth  inch  or  larger,  in 
others.  This  depends  on  the  size  of  the  magneto  and  form  of 
the  pole-piece  lips,  among  other  things.  Sometimes  there  is  a 
reference  mark  to  indicate  the  position  of  the  armature  at  the 
instant  that  the  interrupter  contacts  should  begin  to  separate. 
In  the  absence  of  such  a  mark,  the  instructions  of  the  manu- 
facturer should  be  consulted. 

Either  of  the  following  two  methods  of  timing  the  magneto 
may  be  followed: 

First  Method.  —  Set  the  crank-shaft  of  the  motor  in  the  posi- 
tion through  which  it  is  to  pass  at  the  instant  the  interrupter 


TIMING  THE  IGNITION  401 

contact-points  begin  to  separate  when  the  spark  control  is  set 
for  the  most  advanced  ignition.  This  position  of  the  crank- 
shaft is  somewhat  before  its  dead-center  position  for  the  end  of 
the  compression  stroke  of  one  of  the  pistons  of  the  motor.  It 
may  be  40  degrees  or  more  before  dead  center  for  a  small  high- 
speed motor,  and  10  degrees  or  less  for  a  motor  which  runs  at  a 
very  slow  speed.  (See  later  for  determining  the  corresponding 
position  of  the  piston.) 

Loosen  the  gear  or  coupling  which  drives  the  magneto  rotor  so 
that  the  rotor  can  be  revolved  independently  of  its  driving  shaft 
or  gear. 

Set  the  spark  control  for  most  advanced  ignition,  thus  moving 
the  timing  lever  of  the  magneto  as  far  in  the  direction  opposite 
the  direction  of  rotation  of  the  magneto  rotor  as  it  is  intended 
to  be  moved  while  operating. 

Move  the  magneto  rotor  around  in  the  direction  it  is  to  ro- 
tate, until  the  contact-points  of  the  interrupter  just  begin  to 
separate,  and  the  high-tension  distributer  arm  is  in  position  to 
direct  the  secondary  current  to  the  cylinder  whose  piston  has 
nearly  completed  its  compression  stroke.  Fasten  the  rotor  of 
the  magneto  to  its  driver  in  the  position  thus  determined. 

For  a  motor  which  is  started  by  hand  cranking,  it  should  be 
determined  whether  the  latest  ignition,  as  obtained  by  moving 
the  control  to  its  full  retard  position,  is  late  enough  not  to 
give  a  back-kick  of  the  crank-shaft  when  starting  the  motor. 
The  interrupter  contact-points  can  separate  a  very  short  time 
before  the  crank-shaft  has  reached  dead  center,  without  causing 
a  back-kick,  since  the  movement  of  the  crank-shaft  carries  it 
past  dead  center  before  combustion  can  progress  far  enough 
to  cause  an  appreciable  increase  of  impulse  pressure  on  the 
piston. 

The  method  of  disengaging  the  teeth  of  the  driving  gear,  as 
described  for  timing  a  timer,  can  be  used  if  necessary. 

Second  Method.  —  Set  the  crank-shaft  of  the  motor  in  dead- 
center  position,  with  one  of  the  pistons  at  the  end  of  its  com- 
pression stroke. 

Loosen  the  timer  rotor  from  its  driver. 


402 


ELECTRIC  IGNITION 


Move  the  ignition  control  to  its  position  for  latest  spark. 
This  moves  the  timer  lever  of  the  magneto  to  its  extreme  posi- 
tion in  the  direction  of  rotation  of  the  magneto. 

Move  the  magneto  rotor  to  one  of  the  positions  shown  in 
Fig.  294,  according  to  the  direction  of  rotation  of  the  magneto, 
and  so  that  the  high-tension  distributer  is  in  position  to  direct 
secondary  current  to  the  cylinder  whose  piston  is  at  the  end  of 
its  compression  stroke.  Fasten  the  rotor  to  its  driver  in  the 
position  thus  determined. 

The  distance  E  for  any  magneto  depends  on  the  speed  and 
other  conditions  of  operation.  In  a  small  magneto  it  is  some- 


FIG.  294. 
Position  of  Armature  for  Timing  a  Magneto  by  the  Retarded  Spark  Method. 

times  less  than  one-fifth  of  an  inch,  while  in  a  large  one  it  may 
be  as  much  as  three-fourths  of  an  inch. 

The  value  of  E  should  be  obtained  from  the  manufacturer's 
instruction  book  for  the  magneto  that  is  to  be  timed.  £  is,  or 
should  be,  always  greater  than  A  of  Fig.  293  for  a  given  speed 
of  rotation  of  any  particular  magneto. 

240.  Relative  Positions  of  Crank-Shaft  and  Piston.  —  The  dis- 
tance of  the  piston  of  a  motor  from  the  extreme  end  of  a  stroke 
is  frequently  given  in  connection  with  the  timing  of  ignition. 
The  following  formulas  can  be  used  for  determining  this  dis- 
tance in  a  motor  whose  cylinder  is  not  off-set  to  one  side  of  its 
crank-shaft. 


TIMING  THE  IGNITION  403 

Notation  for  formulas: 
R  =  radius  of  crank, 

=  one-half  the  length  of  the  stroke; 
n  =  ratio  of  the  length  of  the  connecting  rod  to  the  radius  of 

the  crank; 
S  =  angle,  not  greater  than  90  degrees,  of  the  crank-shaft  from 

its  nearest  dead-center  position; 
x  =  distance  of  the  piston  from  its  extreme  position  farthest 

from  the  crank-shaft,  i.e.,  from  its  head  dead-center 

position  in  a  single-acting  motor  of  the  usual  type ; 
y  =  distance  of  the  piston  from  its  extreme  position  nearest 

to  the  crank-shaft. 

For  the  distance  from  the  head  dead-center  position, 
x  =  R\  vers  9  +  n  X  versed  sine  of  the  angle  whose  sine  is 

sin  0~\ 
n   \ 

And  for  the  distance  from  the  crank  dead-center  position, 
y  =  R\  vers  6  —  n  X  versed  sine  of  the  angle  whose  sine  is 

sin  01 
n  _ 


The  only  difference  between  these  two  formulas  is  in  the  plus 
and  minus  signs.* 

As  a  concrete  case  of  application  of  the  formulas,  the  length 
of  the  connecting  rod  will  be  taken  as  four  times  the  radius  of 
the  crank.  This  makes  n  =  4.  And  the  angle  of  the  crank 
from  head  dead-center  position  will  be  taken  as  30°  =  6.  Then, 
by  substituting  these  values  of  n  and  6  in  the  first  formula: 

x  =  R\  vers 30°  +  4  X  vers  of  the  angle  whose  sine  is —  • 

L  4     J 

The  versed  sine  of  30°  is  .134. 

*  Either  of  these  two  formulas  could  be  used  for  any  position  of  the  crank  and 
the  corresponding  position  of  the  piston  (for  any  value  of  6),  but  on  account  of 
the  liability  to  confusion  when  using  values  of  6  greater  than  90  degrees,  it  is 
simpler  to  limit  0  to  a  maximum  of  90  degrees  and  use  both  formulas. 


404  ELECTRIC  IGNITION 

sin 


The  sine  of  30°  is  .500;  therefore 

4 

The  versed  sine  of  the  angle  (about  7°)  whose  sine  is  .125 
is  .008. 

The  last  expression,  therefore,  becomes 

x  =  R  [.134  +  4  X  .008] 
=  R  (.134  +  -032) 
=  .166  R. 

And  since  R  =  half  the  length  of  the  stroke,  2  R  =  length  of 
stroke,  and 

x  =  .083  X  2  R 
=  .083  X  length  of  stroke. 

This  shows  that  the  piston  is  .083  =8.3  per  cent  of  its  full 
stroke  from  the  head  end  of  the  cylinder  when  the  crank  is 
30  degrees  from  its  head  dead-center  position,  and  the  connect- 
ing rod  is  four  times  as  long  as  the  crank  radius,  as  assumed. 

If  the  stroke  of  the  piston  is  6  inches,  then  the  linear  distance 
of  the  piston  from  the  head  end  of  its  stroke  is 

x  =  .083  X  6  =  .498  inch, 

which  is  almost  half  an  inch. 

For  the  distance  of  the  piston  from  the  crank  end  of  its  stroke 
when  the  angle  of  the  crank  is  30  degrees  from  head  dead- 
center, 

y  =#(.134-  .032) 
=  .102  R 
=  .051  X  length  of  stroke. 

And  the  distance  of  the  piston  from  the  crank  end  of  its 
stroke  is 

y  =  .051  X  6  =  .306  inch 

for  the  assumed  6-inch  stroke. 

The  positions  of  the  piston  for  any  crank  angle  up  to  90 
degrees  can  be  found  by  substituting  the  assumed  value  of  the 
crank  angle  in  the  equations  and  solving  in  a  similar  manner. 


CHAPTER  XXVIII. 
IGNITION-SYSTEM  FAULTS  AND  REMEDIES. 

241.  Defects  and  Conditions  in  the  Ignition  System  Which 
Cause  Faulty  Ignition.  —  In  some  cases  a  remedy  is  given  for 
the  trouble  mentioned,  but  in  others  the  remedy  is  so  obvious 
that  it  is  not  mentioned. 

In  the  Igniter. 

242.  Spark-gap   too  wide   or   too   small.     The   spark-points 
sometimes  burn  off  in  magneto  ignition  systems. 

Carbon  and  oil  deposit  in  the  spark-gap  or  on  the  insulation. 
Caused  by  too  much  lubricating  oil  or  a  poor  quality  of  oil,  or 
by  too  rich  a  mixture. 

Water  on  the  spark-points.  Generally  due  to  a  cracked  or 
porous  cylinder.  The  water  may  be  due  to  some  other  source 
when  the  engine  has  been  standing  idle  for  a  considerable 
time. 

Loose  contact-points  in  a  make-and-break  igniter. 

Porcelain  insulation  cracked  or  chipped.  Steatite  insulation 
seldom  cracks  or  chips.  An  igniter  in  this  condition  may  give 
a  good  spark  or  arc  while  the  igniter  is  removed  from  the  motor, 
but  when  in  place  the  defect  may  cause  a  short  circuit  so  as  to 
prevent  the  formation  of  an  ignition  arc  or  spark.  This  is  be- 
cause the  electric  resistance  of  the  spark-gap  is  greater  in  the 
compressed  charge  in  the  motor  than  in  the  open  air.  Porce- 
lain insulation  that  is  chipped  at  the  portion  outside  of  the 
motor  will  generally  not  cause  a  short  circuit  while  the  chipped 
surface  is  still  clean,  but  if  it  is  touched  by  one's  hafld  while 
working  around  the  motor,  so  as  to  leave  dirt  on  the  chipped 
surface,  the  dirt  is  apt  to  cause  a  short  circuit  sufficient  to  pre- 
vent ignition,  especially  when  the  motor  is  working  on  full 

405 


406  ,  ELECTRIC  IGNITION 

charges,  although  the  igniter  may  give  a  good  spark  while  re- 
moved from  the  motor.  This  short  circuit  is  most  apt  to  occur 
when  the  chipped  surface  extends  from  the  insulated  spindle  to 
some  of  the  other  metallic  parts  of  the  igniter. 

Mica  insulation  loose  so  that  dirt  can  collect  between  the 
layers,  or  laminations,  of  the  mica.  The  behavior  of  an  igniter 
in  this  condition  is  much  the  same  as  that  of  one  with  solid 
insulation  that  is  cracked  or  chipped.  It  is  generally  not  pos- 
sible to  clean  mica  that  has  become  fouled  in  this  manner.  It 
is  generally  advisable  to  discard  an  ordinary  jump-spark  plug 
that  has  this  defect,  but  in  the  case  of  a  large  make-and-break 
igniter  the  better  plan  is  to  put  in  new  insulation. 

Mica  insulation  rough  from  scraping  or  crumbling.  Crumbled 
mica  is  worthless.  It  has  somewhat  the  appearance  of  worm- 
eaten  wood.  But  when  the  surface  of  the  mica  is  only  roughened 
it  may  be  polished  in  some  cases.  The  rough  surface  collects 
dirt  and  the  final  result  is  a  short  circuit  in  the  igniter. 

Burned  and  pitted  contact-points.  This  prevents  the  contact- 
points  of  a  make-and-break  igniter  from  making  good  metallic 
contact  with  each  other.  Consequently  the  full  strength  of  cur- 
rent does  not  flow  and  the  arc  is  therefore  weak.  This  condi- 
tion causes  sluggish  action  of  a  magnetically  operated  igniter. 

Loose  packing.  This  allows  some  of  the  compressed  charge 
to  escape.  A  hissing  sound  can  sometimes  be  heard.  Lubri- 
cating oil  put  around  the  igniter  will  sometimes  indicate  the 
leak  by  bubbles  or  by  being  blown  off  at  the  leak.  Put  new 
packing  in  a  high-tension  plug.  A  string  of  asbestos  fiber 
wrapped  around  a  fine  copper  wire  (a  commercial  product)  is 
suitable  in  the  absence  of  the  regular  form  of  packing  for  small 
plugs.  A  gasket  made  of  sheet  copper  bent  over  so  as  to  form  a 
deeply  grooved  ring  with  asbestos  in  the  groove  (copper-asbestos 
gasket  or  washer)  is  convenient  when  there  is  no  rubbing  action 
against  the  gasket.  In  a  make-and-break  igniter  it  may  be  only 
necessary  to  tighten  the  movable  electrode  against  its  bearing, 
in  order  to  take  up  end  wear. 

Operating  parts  worn  so  as  not  to  separate  the  contact-points 
wide  enough  to  draw  a  good  arc. 


IGNITION-SYSTEM   FAULTS  AND  REMEDIES  407 

In  the  Spark-Coil. 

243.  Contact-points  at  the  trembler  burned  or  pitted  so  as 
not  to  make  good  electric  contact.  The  most  usual  indication 
of  this  condition  is  irregular  ignition,  sometimes  followed  by 
complete  stopping  of  ignition.  A  contact-point  is  pitted  when 
it  has  small  depressions,  or  pits,  burned  into  it. 

Water  or  dirt  on  contacts  at  trembler.  Water  generally  stops 
ignition  completely.  Dirt  has  much  the  same  effect  as  badly 
pitted  contact-points. 

Contact-points  stuck  together  by  fusing.  This  sometimes 
happens  when  one  coil  acts  for  several  cylinders.  It  also 
sometimes  happens  when  there  is  excessive  sparking  at  the 
contact-points  of  a  trembler  coil  that  is  used  for  only  one 
cylinder. 

Excessive  sparking  at  trembler  contacts.  May  be  due  to  too 
high  voltage  in  the  primary  circuit,  as  when  there  are  too  many 
cells  in  the  battery.  Cut  out  one  or  two  cells  unless  the  number 
is  known  to  be  correct.  All  spark-coils  do  not  operate  properly 
at  the  same  voltage.  If  reducing  the  number  of  cells  does  not 
stop  excessive  sparking,  then  the  trouble  is  probably  due  to  the 
condenser  not  performing  its  function  correctly,  as  on  account  of 
its  insulation  being  broken  down  or  one  of  its  connecting  wires 
broken  or  loose.  If  there  is,  or  should  be,  a  separate  ground 
wire  for  the  condenser,  see  that  the  wire  is  in  place.  Excessive 
sparking  as  stated,  may  also  be  due  to  defective  insulation  in 
either  the  primary  or  secondary  winding  of  the  coil. 

Insulation  broken  down  in  transformer  coil  or  condenser. 
Indicated  by  excessive  sparking  at  trembler  contacts.  May  be 
caused  by  too  high  a  voltage  in  the  primary  circuit.  Also  by 
allowing  the  trembler  to  operate  while  the  secondary  circuit  is 
disconnected,  especially  where  there  is  no  safety  spark-gap  as 
part  of  the  coil.  Repair  should  be  made  by  an  expert,  or  the 
defective  coil  replaced  by  a  new  one. 

Loose  contact-point  on  trembler.  Unusual.  Causes  irregular 
ignition.  Rivet  or  solder  with  hard  solder  (one  which  does  not 
melt  easily),  such  as  that  used  for  silver.  . 


408  ELECTRIC  IGNITION 

Trembler  spring  bent.  May  change  rate  of  vibration  or  en- 
tirely prevent  it.  Straighten  or  put  in  a  new  spring. 

Difference  of  lag  in  producing  ignition  sparks  when  two  or 
more  spark-coils  are  used  on  one  motor.  Adjust  the  tremblers 
to  vibrate  at  the  same  rate,  as  indicated  by  the  pitch  of  the 
sound. 

In  the  Reactance  Coil  (Kick-Coil). 

244.  Defective  insulation.     May  be  caused  by  using  too  high 
voltage.     Causes  a  weak  arc  at  the  contact-points  of  the  make- 
and-break  igniter,  or  entirely  prevents  arcing.     Dirt  between  the 
terminals  may  have  the  same  effect.    A  kick-coil  seldom  gives 
trouble,  however. 

In  the  Timer. 

245.  Dirt  or  grit  between  contact-pieces  prevents  closing  the 
circuit  and  causes  rapid  wear. 

Hard  grease  between  roller  contact-points  prevents  closing 
the  circuit.  Some  grease  that  is  very  soft  while  warm  becomes 
quite  hard  when  cooled,  as  when  the  motor  stands  over  night  in 
a  garage  that  is  not  warmed.  Use  oil  or  semifluid  grease. 

Oil  between  contact-points  which  close  the  circuit  by  pressure 
only  (without  rubbing  or  rolling)  may  prevent  good  electric 
contact. 

Keep  oil  from  contact-points. 

Circuit  closed  at  wrong  time  on  account  of  worn  or  loose 
parts. 

Stationary  timing  part  worn  loose  so  as  to  wabble  and  shake 
about.  This  is  apt  to  cause  irregularity  in  the  time  of  closing 
the  circuit. 

Stationary  rollers  loose  on  pins  which  support  them.  In 
some  designs  where  the  rotor  strikes  stationary  rollers  to  close 
the  circuit,  the  rollers,  when  worn  loose,  move  about  so  as  to 
vary  the  time  of  closing  the  circuit. 

Failure  to  close  the  circuit  on  account  of  worn  or  binding 
parts. 

Spring  weak  or  broken. 

Brush  binding  or  sticking  in  its  holder. 


IGNITION-SYSTEM   FAULTS   AND   REMEDIES  409 

Rotor  shaft  does  not  have  good  electric  connection  with  the 
metal  of  the  motor.  Causes  imperfect  closing  of  the  circuit, 
and  sometimes  there  may  be  complete  failure  to  close  it.  Con- 
sequently the  ignition  spark  or  arc  is  weak  at  times  or  fails 
entirely. 

Circuit  not  closed  at  the  same  instant  relative  to  the  position 
of  each  piston  in  its  stroke.  May  be  due  to  faulty  construction 
or  to  worn  parts. 

Insulated  contact-piece  of  the  rotor  not  in  continuous  contact 
with  the  part  (shaft)  on  which  it  is  mounted.  Generally  due  to 
a  loose  screw  or  other  fastening.  Causes  weak  spark  and  missing 
of  the  spark. 

Rotor  very  loose  on  its  shaft.  In  some  designs  the  rotor  is 
fastened  to  its  shaft  by  a  set-screw  in  such  a  manner  that  when 
the  set-screw  works  loose  the  rotor  can  gradually  move  around 
on  the  shaft.  Such  a  condition  varies  the  time  of  ignition  to 
an  extreme  amount.  If  this  moving  around  occurs  slowly,  it  is 
necessary  to  keep  advancing  the  spark  at  the  corresponding  rate 
to  keep  the  motor  running.  After  that  the  continued  moving 
of  the  rotor  on  its  shaft  will  prevent  ignition  generally. 

In  the  Magneto. 

246.  Dirt  (carbon  dust,  particles  of  metal)  in  the  distributer. 
Due  to  wear  of  rubbing  parts.  Clean  with  a  bristle  brush  and 
piece  of  cloth  without  using  any  liquid  if  possible.  Use  kerosene 
if  found  necessary  to  remove  the  dirt.  Do  not  oil  if  a  carbon 
brush  is  used.  Put  a  small  amount  of  oil  on  the  rubbing  sur- 
faces with  a  cloth  if  a  metal  brush  is  used  to  rub  against  metal. 

Dirt  in  the  interrupter.  Clean  with  a  bristle  brush  and  a 
cloth.  It  is  better  not  to  use  gasoline,  for  although  it  is  excellent 
for  cleaning,  it  leaves  the  rubbing  surfaces  in  poor  condition.  If 
the  gasoline  is  used,  care  should  be  taken  to  see  that  the  rubbing 
surfaces  are  coated  with  a  small  amount  of  lubricating  oil.  Oil 
the  rubbing  surfaces  very  sparingly,  if  at  all.  The  interrupters 
of  some  magnetos  are  self -oiling.  Others  do  not  require  any 
lubricant.  This  is  the  case  when  one  of  each  pair  of  rubbing 
surfaces  is  of  wood  fiber  or  some  similar  material.  The  inter- 


410  ELECTRIC  IGNITION 

rupter  lever  is  sometimes  bushed  with  fiber  where  it  rocks  on 
its  supporting  pin. 

Contact-points  of  interrupter  burned  or  pitted.  Dress  smooth 
and  flat  with  dead-smooth  file. 

Oil,  grease,  or  water  between  contact-points  of  interrupter. 
Grease  prevents  the  points  from  making  good  contact  with  each 
other.  Oil  is  very  apt  to  do  the  same.  Water  prevents  the 
interruption  of  the  current. 

Weak  spring  on  interrupter  lever.  Does  not  press  the  con- 
tact-points together  firmly.  Put  in  a  new  spring  or  bend  the 
old  one  so  that  it  will  press  the  contacts  together  harder.  If  a 
steel  spring  is  very  soft  it  may  be  retempered.  The  retemper- 
ing  can  be  quickly  done  by  one  familiar  with  heat  treatment  of 
high-grade  steel. 

>  Interrupter  lever  binds  on  its  pin.  Refit.  This  should  be 
done  by  a  skilled  mechanic.  A  reamer  of  the  proper  size  will 
enlarge  the  hole  slightly  and  leave  it  in  good  condition.  A 
twist  drill  may  be  used,  but  is  not  so  good.  In  an  emergency  a 
fine-cut  round  file  may  be  used  to  enlarge  the  hole  in  a  fiber 
bushing.  For  hardened  metal,  a  piece  of  fine-grained  emery 
cloth,  or  of  crocus  cloth,  wrapped  around  a  wire,  can  be  used. 
The  part  should  be  very  carefully  cleaned  afterward.  The  pin 
which  supports  the  lever  generally  cannot  be  removed  conven- 
iently for  reducing  its  diameter. 

Interrupter  contacts  do  not  separate  to  the  proper  distance. 
Adjust  them. 

Interrupter  contacts  do  not  separate  at  the  proper  time 
relative  to  the  position  of  the  armature  or  inductor,  according 
to  which  is  the  rotor.  This  cannot  occur  in  a  magneto  whose 
interrupter  is  fitted  to  a  definite  position,  and  which  was  properly 
determined  when  the  machine  was  made.  Otherwise  adjust  the 
interrupter  to  its  proper  position. 

Distributer  not  in  proper  position  relative  to  the  interrupter. 
This  can  be  corrected  by  shifting  the  gears  which  drive  the  dis- 
tributer relative  to  each  other  when  there  are  such  gears  and 
when  the  interrupter  and  distributer  are  on  separate  shafts. 
Take  the  gears  out  of  mesh  and  advance  or  retard  one  relative 


IGNITION-SYSTEM   FAULTS  AND  REMEDIES  411 

to  the  other  by  the  amount  of  one  tooth,  or  several  teeth,  as 
seems  necessary. 

Roller  or  rollers  of  interrupter  worn  flat  on  one  side.  If  the 
roller  can  rotate,  it  will  cause  the  contact-points  to  separate 
farther  at  one  time  than  at  another. 

Too  much  lubricating  oil.  If  the  oil  reaches  the  insulation  of 
the  armature,  it  is  apt  to  destroy  its  insulating  property  to  some 
extent,  and  a  short  circuit  may  result. 

Brush  (carbon)  worn  out  or  binding  in  its  holder  so  as  not  to 
make  good  contact.  File  the  brush  a  little  smaller  if  it  binds. 

Brush  spring  weak.  Stretch  it  if  it  is  a  coiled  compression 
spring.  Cut  off  some  of  it  if  it  is  a  coiled  tension  spring.  Bend 
a  flat  spring  so  that  it  will  press  harder  against  the  brush  or  its 
holder,  as  the  case  may  be.  Retemper  a  steel  spring  if  thought 
necessary. 

Condenser  insulation  defective,  or  the  condenser  has  loose 
connection.  Excessive  sparking  at  the  interrupter  is  the  result 
of  either  of  these  defects.  The  connection  can  sometimes  be 
easily  tightened  or  repaired,  but  the  defective  insulation  re- 
quires the  attention  of  an  expert. 

Armature  insulation  damp  or  wet.  Remove  the  armature 
and  bake  it  in  a  moderately  warm  place  for  a  day  or  more. 
Then  varnish  the  insulation  with  waterproof  insulating  varnish 
if  it  appears  necessary.  A  magnet  keeper  should  be  placed 
across  the  pole-pieces  when  the  armature  is  removed,  and  left 
there  till  the  armature  is  replaced.  A  flat  piece  of  soft  steel  a 
quarter-inch  or  so  thick  will  answer.  Several  pieces  of  small, 
flat  bar  steel  or  iron  can  be  used  in  the  absence  of  a  larger  piece. 

Armature  insulation  defective.  Requires  the  attention  of  an 
expert. 

Poor  ground  connection  between  armature  and  frame  of 
motor.  This  of  course  does  not  include  machines  in  which  the 
armature  winding  is  intended  to  be  entirely  insulated  from  the 
frame.  Is  apt  to  occur  in  a  machine  which  has  no  ground  brush 
for  a  rotating  armature.  May  be  due  to  the  ground  brush  be- 
coming worn  out,  or  to*  a  loose  connection  between  the  brush 
and  ground. 


412  ELECTRIC  IGNITION 

Bearings  worn  so  that  rotor  strikes  the  pole-pieces. 

Loose  driving  gear  or  coupling.  Tighten  and  fit  new  pin  or 
key  if  the  old  one  is  worn. 

Defective  switch.  May  make  a  partial  ground  connection 
when  the  switch  is  open  and  there  should  be  no  such  circuit. 
The  switch  may  be  only  in  need  of  cleaning. 

Magnets  have  become  weak.  Sometimes  caused  by  removing 
the  rotor  (armature  or  inductor)  without  putting  a  keeper  across 
the  pole-pieces  or  the  ends  of  the  magnets.  The  magnets  can  be 
remagnetized  by  wrapping  insulated  wire  around  them  in  the 
manner  indicated  in  Fig.  50.  It  may  be  necessary  to  take  a 
compound  magnet  apart  and  deal  with  the  magnets  individually. 
The  wire  can  be  wound  from  end  to  end  of  the  magnet  if  de- 
sired, or  it  may  be  put  on  only  one  leg.  A  coil  wound  on  a  non- 
magnetic spool  of  a  shape  to  fit  fairly  closely  to  the  bar  of  the 
magnet  is  convenient.  If  a  spool  is  put  over  each  leg,  the  con- 
nection between  the  spools  must  be  made  so  that  the  current 
will  flow  through  them  in  the  directions  indicated  in  Fig.  50.  A 
piece  of  iron  or  soft  steel  should  be  placed  across  the  ends  of  the 
magnet  legs  in  the  manner  of  a  keeper.  The  electric  current 
needs  to  flow  only  a  second  or  so,  and  should  then  be  decreased 
gradually.  A  gradual  decrease  of  current  can  be  obtained  by 
slowly  separating  two  wire-ends  so  as  to  draw  an  arc  that  grad- 
ually decreases  in  volume  as  the  ends  are  moved  farther  apart; 
or  by  separating  the  wire-ends  gradually  under  impure  water, 
such  as  that  containing  salt  or  acid.  Several  applications  of 
current  may  be  advantageous.  The  strength  of  the  magnet  can 
be  tested  by  its  lifting  power,  as  by  placing  a  heavy  piece  of  steel 
or  iron  on  weighing  scales,  and  noting  the  decrease  of  scale 
reading  when  the  magnet  is  applied  to  lift  the  piece,  after  the 
current  has  been  stopped. 

The  current  used  is  large  enough  when  an  increase  of  it  pro- 
duces no  further  increase  in  the  strength  of  the  magnet,  as 
measured  after  the  current  is  discontinued.  Care  should  be 
taken  to  put  the  individual  magnets  together  so  that  all  of  the 
north  poles  are  next  to  the  same  pole-piece. 


IGNITION-SYSTEM  FAULTS  AND   REMEDIES  413 

In  the  Dynamo. 

247.  Excessive   sparking   at   the   brushes.     Brush   does   not 
make  good  contact  with  the  commutator.     Brush  worn  crooked. 
Roughened   commutator.     May  also  be  due  to  some  of  the 
causes  mentioned  below. 

Armature  coil  burned  out  or  its  insulation  defective.  Causes 
excessive  sparking  at  the  brushes  and  at  one  or  two  segments  of 
the  commutator.  The  commutator  segments  connected  to  the 
defective  coil  appear  burned  at  the  edges. 

Commutator  burned  along  edges  of  all  segments.  Brushes  not 
set  in  proper  position,  thus  causing  sparking  and  burning  at  all 
of  the  segments.  Adjust  the  brush-holder  rotatively  so  as  to 
bring  the  brushes  in  proper  position  if  possible.  Some  dynamos 
have  no  means  of  adjusting  the  brush-holder  in  this  manner. 

Commutator  worn  out  of  round.  Causes  sparking.  If  very 
bad,  turn  true  in  a  lathe.  Can  be  trued  somewhat,  and  smoothed, 
by  sandpapering  with  fine-grained  sandpaper,  after  removing  the 
brushes  from  contact  with  the  commutator. 

Grease  and  dirt  on  commutator.     Causes  sparking  and  burning. 

Brush-holder  dirty.  Causes  a  partial  short  circuit  and  some- 
times heating  of  the  armature  by  the  excessive  amount  of  current 
that  flows  on  account  of  the  partial  short  circuit.  Sparking  and 
burning  of  the  commutator  may  accompany  this  action. 

Field-coil  connection  broken.  This  may  be  inside  of  the  in- 
sulation, but  only  in  unusual  cases.  Prevents  the  generation  of 
current  completely  if  the  ends  are  separated  at  the  break.  But 
if  the  ends  touch  each  other,  there  may  be  indifferent  generation 
of  current. 

Other  troubles  may  be  of  the  same  general  nature  as  some  of 
those  in  a  magneto.  (See  "In  the  Magneto"  immediately  pre- 
ceding.) 

In  the  Battery. 

248.  Exhausted  dry  cells.     If  there  are  two  dry  batteries  and 
both  are  exhausted  so  that  neither  will  supply  sufficient  current, 
put  the  two  batteries  in  series  with  each  other.     As  a  last  resort, 
dig  some  of  the  sealing  compound  from  the  top  of  each  cell  so 


414  ELECTRIC  IGNITION 

as  to  expose  the  blotting  paper,  and  put  water  in  each  cell,  or 
sal  ammoniac  and  water  solution  such  as  is  used  for  the  elec- 
trolyte. Keep  the  paper  covering  of  the  cells  dry. 

Wet  coverings  on  dry  cells.  If  the  paper  covers  become  wet, 
keep  the  cells  separated  so  that  the  covers  cannot  touch  each 
other.  Do  not  let  the  cells  rest  against  metal  or  water-soaked 
wood. 

Storage  battery  discharged.  Indicated  by  low  voltage  of 
battery  while  discharging.  Recharge  the  battery.  Do  not  put 
storage  batteries  in  series  with  each  other  to  secure  a  higher 
voltage  after  the  battery  voltage  has  become  low,  as  just  stated, 
except  in  extreme  emergency. 

Wrong  connections  between  cells  or  batteries.  A  reversed 
cell  reduces  both  the  voltage  and  current  of  the  battery.  Some 
wrong  connections  cause  the  battery  to  run  down  rapidly. 

Cells  loose  so  that  they  can  shake  about.  Is  apt  to  loosen  the 
connections  or  break  them. 

Loose  connections  between  cells.  Causes  erratic  ignition. 
Tighten  the  nuts  of  dry  cells  with  pliers,  or  flatten  the  nut 
slightly  with  a  hammer  so  that  it  binds  on  the  thread.  The 
nut  may  be  secured  with  a  drop  of  solder.  These  methods  are 
suggested  for  dry  cells  only. 

Corroded  terminals.  These  are  apt  to  make  the  connection 
poor  on  account  of  high  resistance.  Clean  and  brighten  the 
metal.  Cover  with  vaseline  or  varnish. 

Dirt  on  insulation  between  terminals.  Causes  leakage  and 
waste  of  current,  especially  if  the  dirt  is  moist. 

Metal  of  adjacent  cells  in  contact.  This  may  occur  between 
the  terminals  or  metal  cans  of  dry  cells.  Wastes  current  and 
reduces  voltage. 

Metal  tools  or  other  metallic  appliances  on  and  against  the 
battery  is  apt  to  cause  a  short  circuit. 

Electrolyte  low  in  cells,  or  not  of  proper  strength  (specific 
gravity,  density). 

Sediment  in  bottom  of  the  cells  of  a  storage  battery.  The 
battery  runs  down  rapidly.  Causes  excessive  heating  of  the 
battery  in  extreme  cases. 


IGNITION-SYSTEM   FAULTS  AND  REMEDIES  415 

In  the  Connections. 

249.  Loose  strand  of  wire  cable.  Is  apt  to  touch  some  metal- 
lic part  so  as  to  make  a  ground  connection  or  a  short  circuit. 
The  strands  of  the  cable  should  be  twisted  together  where  it  is 
bared  to  fasten  to  a  binding  post.  It  is  sometimes  advisable  to 
solder  the  strands  together  where  they  are  bared. 

Swinging  or  vibrating  wire.  If  the  wire  strikes  or  rubs  against 
anything,  the  insulation  will  generally  be  worn  off.  Contact 
with  a  metal  part  and  intermittent  short-circuiting  may  result, 
thus  causing  irregular  ignition. 

Oil  on  insulation  destroys  it. 

Loose  binding  screws  and  joints. 


CHAPTER  XXIX. 

OPERATING  TROUBLES  POSSIBLY  DUE  TO  THE  IGNITION 

SYSTEM. 

250.  Introductory.  —  While  any  of  the  following  troubles  may 
be  due  to  a  faulty  ignition  system,  there  are  also  other  causes  of 
faulty  ignition  to  which  the  trouble  may  be  due,  some  of  which 
are  mentioned  in  each  case.     The  ignition  system  is  referred  to 
only  in  a  general  way  when  the  trouble  may  lie  in  it  on  account 
of  any  or  several  of  the   causes  mentioned  in  the  preceding 
chapter. 

Motor  Will  Not  Start. 

251.  Ignition  switch  not  closed,  or  trouble  in  the  ignition 
system. 

Fuel  valve  closed,  or  no  fuel. 

Compression  valve  open  sometimes  prevents  starting. 

Mixture  not  properly  proportioned.  Generally  too  lean  when 
this  occurs.  Partly  close  the  air  inlet  when  there  is  a  carbureter. 
This  can  be  done  safely  with  one's  hand  for  small  motors. 
Prime  the  motor  cylinders  when  liquid  fuel  is  used. 

Cold  motor.  If  the  starting  methods  just  given  fail,  warm 
the  motor.  Put  hot  water  in  the  jacket  space  or  blow  steam 
into  it.  A  torch  may  be  used,  with  care  not  to  burn  insulation 
or  injure  other  parts,  in  case  of  urgent  emergency. 

Water  or  moisture  in  cylinder.  Remove  the  igniters  and  dry 
the  ignition  points.  Warm  the  motor  cylinder.  It  may  be 
more  convenient  to  blow  air  through  a  large  engine. 

Valve  mechanism  broken  or  valve  timing  wrong. 

Preignition. 

252.  This  is  generally  indicated  by  a  sharp  snapping  sound  or 
heavy  pounding  in  the  motor.     It  is  accompanied  by  the  loss  of 
power.     There  may  be  very  little  sound  to  indicate  preignition 
in  a  very  closely  fitted  motor,  however. 

416 


OPERATING  TROUBLES   DUE  TO  IGNITION  SYSTEM        417 

Ignition  control  advanced  too  far. 

Compression  too  high  for  the  kind  of  fuel  used.  The  normal 
combustible  mixture  for  some  fuels  ignites  by  the  heat  of  com- 
pression at  a  much  lower  compression  pressure  than  others. 

Carbon  deposit  on  the  walls  of  the  combustion  chamber,  in- 
cluding the  head  of  the  piston.  A  projecting  point  or  partly 
loose  flake  of  hard  dry  carbon  becomes  incandescent  and  ignites 
the  charge  early  in  the  compression  stroke. 

Overheating  of  the  cylinder,  piston  head,  exhaust  valve,  igni- 
tion-points or  other  projecting  piece  of  metal  in  the  combus- 
tion chamber. 

In  the  last  two  cases  there  will  generally  be  at  least  a  few 
ignitions  in  the  motor  after  the  ignition  system  is  cut  out  of 
action.  Sometimes  the  motor  will  continue  running  after  cut- 
ting off  the  regular  system  of  ignition. 

Back-firing  into  the  Intake  of  the  Motor. 

253.   Ignition  timing  entirely  wrong. 

Worn  or  loose  part  (as  of  the  timer)  causes  the  ignition  circuit 
to  close  at  the  wrong  time. 

A  condition  under  which  back-firing  is  due  directly  to  the 
ignition  system  is  that  in  which  two  high-tension  spark-plugs 
are  in  series  with  each  other  for  both  cylinders  of  a  two- 
cylinder  four-cycle  motor.  Then,  when  the  ignition  is  very 
much  retarded  while  starting  the  motor,  the  incoming  charge 
for  one  cylinder  is  ignited  at  the  same  instant  as  the  com- 
pressed charge  in  the  other.  This  action  stops  as  soon  as  the 
motor  has  gained  speed. 

Carbon  deposit  on  the  walls  of  the  combustion  chamber,  in- 
cluding the  head  of  the  piston.  Preignition  generally  occurs 
also  in  this  case. 

Overheating  of  the  cylinder,  piston,  ignition  points,  or  exhaust 
valve,  or  of  a  projecting  piece  of  metal  in  the  combustion  cham- 
ber. Preignition  generally  occurs  also. 

Inlet  valve  stem  binding  or  sticking. 

Valve  timing  wrong.     Weak  spring  on  the  inlet  valve. 


418  ELECTRIC  IGNITION 

Lean  mixture.  A  lean  mixture  may  be  due  to  leaks  at  the 
joints  of  the  inlet  pipe  or  manifold.  The  fuel  valve  may  be 
adjusted  to  admit  too  little  gas  fuel,  or  the  carburetor  adjusted 
similarly.  Water  in  gasoline  will  cause  a  lean  mixture  temporarily. 
A  lean  mixture  burns  slowly,  so  that  the  flame  may  continue 
from  one  charge  to  the  next,  thus  igniting  the  incoming  charge. 

Rarefaction  of  the  charge  by  throttling  or  cutting  off  the  com- 
bustible mixture  early  in  the  intake  stroke.  Back-firing  under 
this  condition  is  especially  apt  to  occur  in  a  motor  using  liquid 
fuel  and  a  float-feed  carbureter  in  such  service  as  that  on  an 
automobile  or  a  motor  boat,  when  the  throttle  is  suddenly  nearly 
closed  from  full  open  position  with  the  motor  pulling  hard. 
The  back-firing  under  this  condition  is  probably  due  to  both 
the  rarefaction  of  the  charge  and  leanness  of  the  mixture.  The 
fuel  level  in  the  float  chamber  of  the  carbureter  is  lowered  some- 
what when  the  motor  is  working  at  full  torque  and  high  speed. 
The  reduced  suction  of  the  carbureter,  together  with  the  low 
level  of  the  fuel  in  it,  gives  a  lean  mixture  temporarily. 

Overheating  of  the  Motor. 

254.  Ignition  too  late.     The  exhaust  connections  generally  be- 
come very  hot  under  this  condition,  sometimes  red  hot. 

Mixture  too  rich.  May  be  indicated  by  black  (not  white  or 
blue-white)  smoke.  Exhaust  heats  as  just  mentioned. 

Cooling  medium  (water,  oil,  air)  does  not  circulate  freely. 
May  be  due  to  stoppage  of  passages  or  faulty  action  of  pump  or 
fan.  When  a  motor  car  without  a  fan  climbs  a  long  grade  with 
the  wind  in  hot  weather,  and  with  the  sun  shining  full  on  the 
radiator,  overheating  is  very  apt  to  occur. 

Exhaust  connections  clogged.  This  causes  back  pressure  and 
necessitates  the  burning  of  more  fuel  than  when  the  passages 
are  free. 

Misfiring  and  Exhaust  Explosions  without  Other  Serious  troubles. 

255.  When  there  is  no  back-firing,  and  the  motor  pulls  well 
during  the  intervals  of  no  misfiring,  the  cause  may  be : 

Any  defect  or  improper  condition  of  the  ignition  system. 


OPERATING  TROUBLES  DUE  TO  IGNITION   SYSTEM        419 

Mixture  too  rich.  When  there  is  a  carbureter  for  liquid  fuel, 
this  may  be  caused  by  flooding  of  the  carbureter  on  account  of  a 
sticking  or  binding  float  or  a  leaky  valve  in  the  carbureter. 

Lubrication  of  the  motor  excessive,  or  wrong  kind  of  oil. 

Exhaust  valve  binding  or  sticking. 

Broken  exhaust  valve. 

Knocking  or  Pounding. 

256.  Ignition  control  set  too  early. 

Preignition  on  account  of  carbon  in  the  motor  cylinder,  over- 
heating, or  too  high  compression. 
Loose  bolts  or  other  fastenings. 
Flywheel  loose  on  shaft,  or  cracked. 

Sudden  Stopping  of  Motor. 

257.  Trembler  contacts  stick  together. 

Dirt  between  contact-points  of  any  part  of  the  ignition  sys- 
tem prevents  closing  of  the  electric  circuit. 
Electric  connections  broken  or  loose. 
Valve  binds  or  sticks  so  as  to  remain  open. 
Valve  gear  broken. 

Motor  Does  Not  Develop  Full  Power. 

258.  Ignition  too  late  or  too  early. 
Compression  leaks  prevent  full  compression. 

Particle  of  carbon  under  valve  so  as  to  prevent  its  complete 
closing.  • 

Valve  stem  too  long.  This  may  not  cause  a  leak  until  the 
motor  has  become  hot  from  working  at  full  load  for  some  time, 
and  then  may  disappear  as  soon  as  the  motor  has  cooled  slightly, 
so  that  a  compression  test  does  not  show  the  leak  unless  the  test 
is  made  immediately  after  the  motor  has  been  working  at  full 
load. 

Cracked  cylinder. 

Leaks  around  or  through  the  igniter,  compression  relief  valve, 
piston,  etc. 


420  ELECTRIC  IGNITION 

Mixture  lean  or  too  rich. 

Lubrication  insufficient  or  wrong  kind  of  lubricating  oil. 

Valves  do  not  open  wide  enough. 

Valve  timing  wrong. 

Clogged  exhaust  passages. 

Spark  Control  Must  be  Advanced  More  Than  Usual  and  Motor 
Behaves  Erratically. 

259.  This  is  characteristic  of  a  loose  timer  rotor,  which  is  so 
loose  as  to  drop  back  part  of  a  rotation  on  the  shaft  or  other 
part  that  drives  it.  Irregularity  in  the  time  of  ignition,  which 
is  not  helped  by  advancing  the  control  excessively,  may  be  due 
to  other  loose  parts  of  the  timer  or  corresponding  device. 


INDEX. 


PAGE 

Accumulator  battery  defined 3 

Advance  and  retard,  effect  on  strength  of  ignition  spark 302 

mechanism  for  ignition  spark 306 

Alternating  current  in  shuttle-wound  armature 25 

Ammeter,  dead-beat  needle  for 59 

direction  of  current  determined  with 53 

permanent  in  jump-spark  system 249 

portable 54 

stationary 55 

in  series  with  resistance  for  testing 379 

using 56 

Ampere-hour  defined 109 

Anode 51 

APLCO  electric  system 116 

Apparatus  for  measuring  voltage  and  current 54 

Arc,  position  of  armature  for  maximum : 30 

speed  of  armature  for 15 

from  shuttle-wound  armature 14 

Armature,  alternating -current  type 1 1 

alternating  current  in  shuttle-wound 2$ 

coil,  wire  for 12 

connections  of  direct-current 45 

connections  for  four-pole  generator 71 

core,  laminated 18,  43 

core,  magnetic  flux  in  I-shaped 19 

core,  shuttle  type 12 

current  induced  in  I-shaped 24 

current  represented  graphically 28 

direct-current  type,  complete 44 

direction  of  current  in 26 

drum  type,  current  generated 39 

drum  types 38,  44 

effect  cf  speed  on  position  of  maximum  spark  or  arc 16 

electromotive  force  in  I-shaped 24 

end-piece 13 

of  generator 9 

head 13 

H-type 14 

l-type 14 

421 


422  INDEX 

PAGE 

Armature,  lag  of  current  in 16,  24 

magnetic  flux  through  stationary  shuttle-wound 36 

magneto  rotary 1 1 

positions  for  maximum  spark  affected  by  lag 16 

positions  for  no  spark 16 

position  for  timing  a  magneto 400,  402 

position  of  shuttle-wound  at  instant  of  maximum  arc  or  spark 15,  30 

positions  for  strong  arc  or  spark 16 

reactions,  effect  of 25 

regulating  the  speed  of  direct-current  type 48 

rotary  shuttle-wound n 

reversing  the  rotation  of 76 

shuttle-wound 10 

sparks  per  revolution  of  shuttle-wound : 16 

setting  in  position  in  a  magneto 321 

stationary  shuttle-wound  and  rotary  sleeve  inductor 35 

stationary,  and  inductor .,....,.,.. 298 

shuttle-wound  rotary r ... : n 

speed  for  drawing  an  arc 15 

spindle,  hollow 14 

winding  of 12 

winding  of  direct-current 45 

Automatic  spark-advance  mechanism 113 

Automatic  cut-out  for  protecting  a  generator 113 

Backfiring 417 

Battery,  see  also  Storage  Battery. 

accumulator  type  defined j 

accumulator,  see  Storage  Batteiy. 

care  of,  in  general 374 

connections 88 

connection  to  external  circuit 94 

connections  kept  tight 375 

corrosion  of  terminals  prevented 375 

current  capacity 89 

decrease  of  current  from  primary 80,  82 

defined 3 

depolarization  of 80 

deterioration  of  dry 82 

economy  with  timer  and  contact-maker 260 

electrodes  of ....... 79 

electrolyte  of 79 

exhausted  by  a  reversed  cell 91 

exhaustion  by  wrong  connection 94 

exhaustion  of  dry ...... .... . ... . 83 

floated  on  the  line no 

floated,  switchboard  for  two-voltage  system  with . 121 

lamp  for  testing 381 


INDEX  423 

PAGE 

Battery,  leakage  when  wet 375 

local  action  in 80 

marine 96 

multiple-connected 90 

parallel-connected 90 

parallel-series 92 

polarization  of 79 

primary 78 

primary,  denned •. 3 

recuperation  of  dry 83 

reversed  cell  in 89,  91 

running  down  of  dry 83 

screw-top  connected 95 

secondary,  see  Storage  Battery. 

secondary,  denned -3 

series-connected 88 

short-circuiting  injurious 82 

storage,  secondary,  or  accumulator,  see  Storage  Battery. 

storage  defined ^     3 

switch  in  connections  to  external  circuit 94 

terminals  of 89 

terminals  of  parallel-connected 90 

testing  the  cells  of 381 

testing  a  primary 376 

troubles 413 

voltage  of  parallel-connected 90 

voltage  of  series-connected 89 

water-tight  box  for 96 

without  wire  connections 95 

wrong  connections  for 93 

Battery  cell .    3 

action  of  carbon-zinc  wet 79 

BSCO  wet 84 

capacity  and  dimensions,  table 87 

carbon-zinc,  new  type 82 

carbon-zinc  primary  wet 78 

carbon-zinc  primary  dry 80 

copper  oxide  and  zinc  wet 84 

current  capacity  of  dry 82 

depolarizer  for 81,  84 

Edison  primary  wet 86 

Lalande  and  Chaperon  primary  wet 84 

Leclanche  primary  wet 78 

polarization  of 80 

reversed  in  a  battery 89 

screw-top 95 

terminals  of 79 

voltage  of  carbon-zinc 80 


424  INDEX 


PAGE 


Battery  cell,  voltage  of  dry  carbon-zinc 82 

voltage  of  copper  oxide  and  zinc 86 

wet  primaiy  carbon-zinc 78 

Battery  cells,  current  increase  by  connecting 89,  90 

Brush  of  electric  machine  denned 31 

connecting  rotary  armature  to  frame  of  magneto 32 

material  for  current-carrying 32 

Brushes  for  dynamo 70 

position  in  direct-current  generator 67 

Cam-shaft,  speed  of 147 

Care  and  adjustment  of  ignition  systems 368-377 

Cathode 51 

Cell  of  battery 3 

Coil,  induction,  see  Spark-coil. 

Condenser,  auxiliary  in  ignition  system 242,  247 

grounded  in  ignition  system 243,  247 

use  of,  in  spark-coil 206 

Combustion,  varying  time  of  ignition  relative  to  rate  of 362 

Commutator,  care  of 373 

of  direct-current  generator 41,  44 

lubricating  the 373 

Compass  needle,  extemporized 53 

Compass  test  for  direction  of  current 52 

Connections,  keeping  tight 375 

trouble  in  the 415 

Contact,  duration  of,  in  mechanically  operated  igniter 126 

duration  of,  in  make-and-break  igniter 145,  147 

Contact-maker,  mechanically  operated  for  jump-spark  ignition 254 

snap-spring  type 254 

Contact-points,  filing  or  dressing 374 

life  increased  by  using  two  pairs  of 175 

magneto,  adjusting 373 

repairing 369,  374 

Core-neck  of  armature 12 

Crank-shaft  and  piston,  relative  positions  of 402 

Current,  affected  by  form  of  pole-pieces 29 

alternating,  in  shuttle-wound  armature 25 

ammeter  test  for  direction  of 53 

automatic  regulation  of  direct,  in  dynamo 73 

color  test  for  direction  of 51 

cycle  of  alternating 29 

cycles  of,  in  stationary  shuttle  armature  with  rotary  sleeve  inductor 37 

direction  tests 50 

direction  determined  by  compass  needle 52 

direction  of,  in  armature 26 

in  drum  armature 39 

economy  with  timer  and  contact-maker  compared 261 


INDEX  425 

PAGE 

Current,  graphical  representation  of,  in  shuttle  armature 28 

induced,  in  I-shaped  armature 24 

lag  of,  in  armature 24 

magnetic  needle  test  for  direction  of 52 

testing  for  direction  of 50 

voltmeter  test  for  direction  of 53 

water  test  for  direction  of 50 

Current  capacity  of  a  battery 89,  90 

Current  supply  system,  APLCO 1 16 

apparatus  for  two- voltage,  with  floated  battery 122 

automatic  cut-out  for 114 

battery  floated  on  the  line no 

Dayton  Electrical  Manufacturing  Company 122 

dynamo  and  floated  battery no,  122 

dynamo,  storage  battery  and  switchboard  for 122 

generator  and  two  floated  batteries 117 

switchboard  for  two-voltage 119 

two-voltage,  batteries  floated 117 

volt-ammeter  included 1 16 

Cut-out,  automatic,  for  protecting  dynamo 73,  113,  121 

Cycle  of  current 29 

Density  and  hydrometer  scales  compared,  table 385 

Distributor,  high-tension 252,  253 

spark-coil  and  contact-maker  combined 259 

Dual  ignition  system,  low-tension  electromagnetic 171 

plunger-core  electromagnets  in 171 

Dynamo,  Apple  Electric  Company,  four-pole 73 

armature  connections  for  four-pole 71 

automatic  cut-out  for 73 

bipolar  shunt-wound 65 

brushes  for 70 

brushes,  position  of 67 

building  up  of  pressure  in 66 

capacity  of 70 

care  of 372 

compound-wound 74 

current  automatically  regulated 73 

current  in  field-coils  of 65 

Dayton  Electrical  Company's  bipolar 68 

defined 3 

direct-current  shunt-wound 65 

electromagnets  for 62 

field-coils  for 69 

four-pole 71 

speed  governor  for 71 

shunt-wound 65 

troubles 413 


426  INDEX 

PAGE 

Electricity,  high-tension,  defined -      t 

low-tension,  defined ;  I 

sources  of,  for  ignition 3 

Electric  cell 3 

Electric  measuring  instruments 54 

Electric  generator 3 

armature  of 9 

field-magnets,  electromagnetic 62 

field-magnets,  permanent 8 

inductor  of 9 

principle  of 8 

troubles 409,  413 

Electric  supply,  see  Current  Supply  Systems. 

Electric  system,  battery  floated  on  the  line no 

two-voltage  batteries  floated  on  the  line 117 

two- voltage,  floated  batteries,  lamps  and  ignition  apparatus 119 

Electrode 51 

Electrodes  of  a  battery 79 

Electrolyte 51 

of  a  battery 79 

density  of 386 

density  of,  testing 384 

hydrometer  for  testing  the 384 

mixing  of 392 

Electromagnets,  see  also  Magnets. 

Electromagnets 60 

Electromagnet,  bar-shaped 60 

compound-wound 74 

consequent  poles  in 62 

four-pole,  ring-shaped 63 

plunger-core  type 61 

polarity  relative  to  current 60 

residual  magnetism  in 60 

ring-shaped 62 

ring-shaped  four-pole 63 

U-shaped 62 

Electromagnetic  igniters,  low-tension 169,  199 

Electromotive  force  in  a  generator 8 

induction  of 9 

induction  of,  in  an  I-shaped  armature 24 

of  carbon-zinc  wet  battery  cell ; 80 

Explosions  in  the  exhaust 418 

Field,  magnetic '    6 

Field-coils 69 

current  in 65 

rheostat  in  series  with , 75 

Field-magnets. .,,,,.,,...., 10 


INDEX  427 

PAGE 

Field-magnets,  abutted 1 1 

four-pole  ring-shaped 63 

ring-shaped 62 

U-shaped 62 

Flux,  magnetic 6 

magnetic,  in  I-shaped  armature  core 19 

methods  of  varying  magnetic 9 

variation  of,  to  induce  electromotive  force 9 

Generator,  Apple  Electric  Company's  four-pole 73 

armature  connections  of  direct-current 45 

armature  connections  for  four-pole 71 

armature  for  direct-current 44 

armature  of  electric 9 

automatic  cut-out  for 73 

bipolar  electromagnetic 65 

building  up  of  pressure  in  an  electromagnetic 66 

brushes  for  commutator  of 70 

brushes,  position  of,  for  direct-current 67 

capacity  of  direct-current 70,  148 

care  of  electric 372 

commutation  of  current  in 41 

commutator  of  direct-current 41 

compound-wound  direct-current 74 

current  automatically  regulated 73 

Dayton  Electric  Company's  direct-current 68 

direct-current  electromagnetic 65 

direct-current  elementary ,  „ 42 

direct-current  four-pole 71 

direct-current  shunt- wound 65 

direct-current  type 38 

direct-current  type,  with  permanent  magnets 38 

electric 3 

electromagnetic,  denned 3 

electromagnetic,  field-magnets  of 65 

electromagnetic,  time  required  to  build  up  voltage 148 

electromagnets  for 62 

field-coil  current 65 

field-coils  for 69 

field-magnets,  electromagnetic 62 

field-magnets,  permanent 8 

floated  storage  battery,  lamps  and  ignition  apparatus 114 

four-pole  direct-current 71 

inductor  of  electric 9 

pressure  regulation  in  electric, 75 

principle  of  electric ..  8 

reversing  the  rotation  of 76 

rheostat  for  regulating  voltage  of 75 


428  INDEX 

PAGE 

Generator,  shunt-wound  direct-current 65 

shunt- wound  four-pole 71 

speed  governor  for 71 

storage  battery  and  lamp no 

troubles  in  electric 409,  413 

Governor  for  regulating  speed  of  armature 48 

Ground  brush  in  a  magneto 32 

Ground  connection  defined 144 

H-armature 14 

High-tension  electricity  defined I 

Hydrometer  scale  compared  with  density,  table 385 

Hydrometer  for  testing  electrolyte 384 

I-armature 14 

Igniters:   Make-and-break  igniters  are  indexed  under  Igniters;   jump-spark 
igniters  are  indexed  under  Spark-plugs. 

Igniter,  action  of  make-and-break 145 

action  indicated  by  tell-tale  kick-coil 143 

advance  and  retard  control  of  mechanically  operated  make-and-break     123,  136 

Allis-Chalmers  for  large  engine 184 

automatic  control  of  mechanically  operated 131 

Bosch  electromagnetic,  small 192 

Bosch  mechanically  operated 126 

contact  duration  in  mechanical  make-and-break 126 

contact-point  material 126 

contacts,  repairing 370 

control  for  mechanically  operated 128,  136 

electromagnetic  double-contact,  large 176 

electromagnetic,  large 184 

electromagnetic  low-tension,  small 191 

electromagnetic  of  Wisconsin  Engine  Company 175 

electromagnetic,  operation  of 169 

elements  of  low-tension  mechanically  operated 123 

Fay  &  Bowen  mechanically  operated 131 

hammer-break  in 125 

low-tension  electromagnetic,  small 191 

low-tension  mechanically  operated,  elements  of 123 

make-and-break,  action  of 145 

make-and-break,  duration  of  contact 145,  147 

make-and-break,  double  contact 171 

make-and-break  mechanically  operated,  elements  of 123 

operation  of  electromagnetic 169 

operating  mechanism  of  Snow  Steam  Pump  Works'  mechanical  make-and- 
break 133 

plunger-core  electromagnetic 170 

Snow  Steam  Pump  Works'  mechanically  operated 133 

Truscott  Boat  Manufacturing  Company's  mechanically  operated 128 


INDEX  429 

PAGE 

Igniter,  Westinghouse  mechanically  operated 132 

Igniters,  advance  and  retard  control  for  mechanically  operated 138 

electromagnetic,  low-tension 169-199 

engine  showing  mechanically  operated  igniters  in  place 138 

low-tension  mechanically  operated 123-139 

make-and-break  mechanically  operated 123-139 

mechanically  operated  in  place  on  engine 138 

operating  mechanism  for  mechanical  make-and-break 137 

successive  order  of  action  of 137 

Ignition,  advancing  and  retarding  in  a  variable-speed  motor •   366 

advancing  on  account  of  lag 361 

automatic  advance  and  retard  mechanism 180 

control,  advance  must  be  excessive 420 

coupling  for  varying  time  of 303,  306 

general  methods  of  electric .     I 

high-tension,  denned i 

shaft  coupling  for  varying  time  of 303,  306 

low-tension,  defined •  I 

manipulation  of,  in  an  automobile  motor 366 

premature 416 

three  igniters  per  combustion  chamber 166 

timing 397-404 

variation  of,  reduced  by  simultaneous  sparks 365 

varying  the  time  of 361-367 

varying  the  time  on  account  of  lag 361 

varying  the  time  of,  relative  to  combustion  rate 362 

varying  the  time  of,  relative  to  speed 364 

varying  the  time  of,  in  a  variable-speed  motor 266 

varying  the  time  of,  with  shaft  coupling 303,  306 

Ignition  spark,  means  of  obtaining  constant  strength  of 302 

strength  affected  by  advance  and  retard 301 

Ignition  sparks,  simultaneous 365 

Ignition  systems,  see  also  Current  Supply  Systems  for  source  of  electricity. 

Ignition  systems,  high-tension  dual  and  combined .  .  .- 326-352 

low-tension,  electromagnetic  igniters 169-199 

low-tension  mechanical  make-and-break 144-168 

magneto  current  only 268-325 

jump-spark  with  trembler  interrupters  and  individual  spark-coils . .     240-251 

jump-spark,  distributor  and  battery 252-260 

Ignition  system,  action  indicated  by  tell-tak  kick-coil 143 

Allis-Chalmers  electromagnetic 189 

battery  in  series  with  magneto  primary 345 

Bosch  dual 340 

cam-shaft  speed 147 

charged  and  discharged  condenser  for  constant  strength  of  spark 302 

condenser  auxiliary 242,  247 

condenser  grounded  in  jump-spark .».. 243,  247 

connections  kept  tight 375 


430  INDEX 

PAGE 

Ignition  system,  dual  Bosch  high-tension 340 

dual  electromagnetic  low-tension 171 

dual  electromagnetic  for  large  engine,  low- tension 189 

duplex  Bosch  high-tension 345 

electromagnetic  dual 171 

electromagnetic  make-and-break,  with  magneto 194 

Eisemann-Carpentier  high-tension 337 

Eisemann  high-tension 334 

faults  and  remedies 405-415 

flash  lamps  in  low-tension 174,  184 

high-tension  Eisemann 334 

high-tension  Eisemann-Carpentier » 337 

high-tension  Remy 327 

high-tension  Splitdorf,  separate  transformer 330 

24  igniters  for  one  engine 166 

interrupted  magneto  current 268 

interrupted  magneto  shunt  current 271 

jump-spark,  auxiliary- condenser 242,  247 

jump-spark,  distributor  and  battery 252 

jump-spark  with  ammeter  and  voltmeter  permanently  connected 249 

jump-spark  with  grounded  condenser 243 

jump-spark,  synchronized 245 

jump-spark,  one-unit  trembler  spark-coil 240 

jump-spark,  trembler  coil 252 

jump-spark  with  individual  trembler  coils 244 

low-tension  dual  electromagnetic 171,  189 

low-tension  four-ring  timer 189 

magnetic  plug  and  magneto 194 

magneto  with  double- wound  high-tension  armature 273 

mechanical  make-and-break,  alternating  magneto  current,  elementary. .  146 

mechanical  make-and-break,  battery  current,  elementary 144 

mechanical  make-and-break,  direct-current  generator,  elementary 148 

mechanical  make-and-break,  four-cylinder,  elementary 149 

mechanical  make-and-break,  using  no-volt  current  152-165 

mechanical  make-and-break,  with  switchboard 152 

shunted  magneto  current 272 

Remy  high-tension 327 

series-shunt  spark-plugs 261 

spark-plugs  in  series 261 

switchboard,  one-unit 152 

synchronism  of  magneto  in 147 

synchronized  jump-spark 245 

triple  low-tension  mechanical 166 

i lo-volt  not  grounded 162 

Ignition  apparatus,  adjustment  and  care  of 368 

Induction  coil,- see  Sparkrcoil. 

Inductor  of  electric  generator 9 

rotary  sleeve, type 35 


INDEX  431 

PAGE 

Inductor,  rotary  and  stationary  armature 298 

sparks  per  revolution  of  sleeve  type 37 

Instruments  for  measuring  voltage  and  current 54 

Interrupter,  Mea  type 319 

mechanically  operated  for  battery  current 254 

mechanically  operated  in  magneto 319 

setting  device  for 290 

of  spark-coil,  see  Trembler. 

U.  &  H.  magneto 289 

Interrupters,  two  on  one  magneto 342 

Keeper  of  magnet 6 

Kick-coils 138 

Kick-coil,  action  of 145 

screw-top  type 142 

with  switch  and  key  lock 347 

tell-tale  for  indicating  action  of  igniter 142 

troubles 408 

waterproof 140,  141 

Kick-switch  for  spark-coil 222 

Knocking  or  pounding  in  the  motor 419 

Lag  of  armature  current 24 

of  electric  current  in  a  magneto 16 

of  spark  from  a  magneto 16 

of  spark-coils 214 

Lalande  and  Chaperon  wet-battery  cell 84 

Lamination  of  armature  core 18 

Lamps  used  as  resistance 2,  152,  388 

Low-tension  electricity  defined i 

ignition  system,  flash  lamps  in 174 

Magnets,  see  also  Electromagnets. 

Magnet,  action  on  compass  needle 5 

determination  of  N  and  S  poles 5 

keeper 6 

poles  of , 5 

poles,  consequent 62 

Magnets,  abutted 1 1 

bell-shaped  in  a  magneto 316 

composite 8 

compound 8 

horseshoe  form 4 

for  magneto 8 

method  of  making  permanent 4 

permanent 3 

rocking,  in  a  magneto 316 

U-shaped 8 


432  INDEX 

PAGE 

Magnetic  compass  test  for  direction  of  current 52 

field 6 

field  not  affected  by  non-magnetic  materials 8 

flux 6, 

flux  th'rough  stationary  shuttle  armature  and  sleeve  inductor 36 

flux  in  I-shaped  armature  core 19 

flux,  rate  of  change  in  I-shaped  armature  core 22 

flux,  variation  of g 

flux,  methods  of  varying gi 

materials 7 

needle  test  for  direction  of  current 52 

Magnetism,  residual 60 

residual  in  electromagnetic  generator 66 

shield  pole  extensions 311,  314 

sleeve  pole  extensions 311,  314 

sleeve  inductor,  magnetic  flux  through  armature 36 

sleeve  rotary  inductor 35 

Magnetos,  see  also  Dynamo. 

high-frequency  low-tension  alternating-current 353~36o 

Magneto,  advance  and  retard  of  spark,  automatic 306 

alternating  current  in  shuttle-wound 25 

arc  from  shuttle-wound 14 

armature,  setting  to  correct  position 321 

armature  core 12 

armature,  double-wound 273 

armature,  shuttle- wound 1 1 

automatic. advance  .and  retard  mechanism  on 306 

Bosch  duplex 350 

Bosch  high-tension 275 

Bosch  low-tension  alternating-current 31 

care  of ' 372 

charged-and-discharged  condenser  type 302 

defined 3 

detail  description  of  low-tension  shuttle- wound 31 

direct-current  types 38,  47 

Eisemann  high-tension 305 

elementary  shuttle-wound 14 

fastenings  of  magnetic  material  not  suitable 146 

field-magnets,  abutted 1 1 

Ford  high-frequency  low-tension 358 

high-tension 330 

high-tension  Bosch  duplex 350 

high-tension,  with  stationary  armature  and  rocking  pole-pieces 311 

high-tension,  with  commutator  and  interrupter 350 

high-tension,  with  single-wound  armature 272,  307,  310 

high-tension,  double- wound  rotary  armature 275 

high-tension,  with  two  high-tension  windings 352 

high-tension,  with,  magneto  primary  in  series  with  battery  circuit 345 


INDEX  433 

PAGE 

Magneto,  high-tension,  with  separate  transformer 307,  310 

high-tension,  with  two  interrupters 342 

internal  connections  of  low-tension  alternating-current 30 

interrupter  types 268-325 

interrupter  type,  for  electromagnetic  igniters 196 

K-W  high-frequency  low-tension 356 

lag  of  current  in 16 

low-tension  alternating 10 

low-tension  alternating,  sectional  view  of 31 

low-tension,  for  electromagnetic  igniters 196 

low-tension,  with  stationary  armature 354,  356,  359 

magnets  for 8 

magnets  rocked  in 316 

Mea  high-tension,  with  rocking  magnets 316 

Pittsfield  high-tension 311 

Remy 275 

rotary  armature  types 1 1 

with  rotating  magnet  inductor 358 

sectional  view  of  low-tension  alternating-current 31 

shuttle  armature  types 10 

shuttle- wound  low-tension 30 

spark  from  shuttle-wound 14 

speed  for  drawing  an  arc 15 

speed  governor  for  direct-current 48 

Splitdorf  high-tension 330 

Splitdorf  low-tension  alternating-current 34 

starting  device  for 294 

stationary  armature,  high-tension 295 

synchronism  of  alternating-current , 147 

timing  of  a , 400 

troubles 409 

U.  &  H.  high-tension 288 

W.  &  S.  high-frequency  low-tension 353 

Make-and-break  igniters,  see  Igniters. 

Materials,  magnetic 7 

non-magnetic 7 

Measuring  instruments  for  voltage  and  current 54 

Misfiring 418 

Motor,  crank-shaft  and  piston  positions  in 402 

overheating  of  a 418 

full  power  not  developed 419 

knocking  or  pounding  in.  \ 419 

pulls  weakly 419 

stops  suddenly 419 

will  not  start 416 

Multiple  battery,  see  Battery. 

Non-magnetic  materials 7 


434  INDEX 

PAGE 

Oiler,  felt-wick 69 

Overheating  of  the  motor 418 

Parallel  battery,  see  Battery. 

Piston  and  crank-shaft,  relative  positions  of 402 

Plunger-core  electromagnet 61 

Polarization  of  a  battery 79,  80 

Poles  of  a  magnet 5 

Pole-pieces,  crowned 30 

different  forms  of 29 

form  of,  affects  range  of  advance  and  retard  of  spark 30 

form  of,  affects  current  curve 29 

of  magnets 10,  29 

magnetic  sleeve  extensions  of 311,  314 

movable  extensions  of 311,  314 

notched  or  tooth-shaped 30 

rounded 30 

Pole-shoes  of  magnets,  see  Pole-pieces. 

Pounding  or  knocking  in  the  motor 419 

Power  not  fully  developed 419 

Preignition 416 

Pressure,  compound-wound  generator  for  constant 74 

Pressure,  electric,  denned i 

in  low-tension  ignition 2 

Primary  battery  denned 3 

Reactance  coils,  see  Kick-coils. 

Reactions,  effect  of,  in  armature  of  generator 25 

Resistance  for  charging  storage  battery,  computed 389 

for  use  in  series  with  ammeter 379 

lamps  used  for 2,  152,  388 

Reversed  cell  in  a  battery 89,  91 

Rheostat  for  regulating  voltage  of  generator 75 

Safety  spark-gap 213 

Secondary  battery  denned 3 

Secondary  battery,  see  Storage  Battery. 
Series  battery,  see  Battery. 

Shaft  couplings  for  advancing  and  retarding  ignition 303,  306 

Shock,  electric t- 

as  affected  by  condition  of  skin 4 

Short-circuiter,  high-tension 264,  266 

Spark  advance  and  retard  affected  by  form  of  pole-pieces 30 

advancing  and  retarding  in  a  variable-speed  motor 366 

constant  strength,  means  of  obtaining 302 

manipulation  of,  in  an  automobile  motor 366 

positions  of  armature  for  maximum 30 

from  shuttle-wound  armature 14 


INDEX  435 

PAGE 

Spark,  speed  of  armature  for  drawing 15 

strength  affected  by  advance  and  retard  of 301 

timing  of  the  ignition 397-404 

Sparks  per  revolution  of  shuttle  armature 16 

per  revolution  of  sleeve  inductor 37 

Spark-coil,  adjusting  trembler  of 370 

Autocoil  Company 216 

condenser  of 206 

connections  of 203 

elementary  forms  of 200 

high-tension,  with  switch  and  key  lock 343 

kick-switch  type 222 

laboratory  type 218 

lag  of 214 

lag,  obviation  of  unequal 222 

master  type  for  synchronizing. 222 

non-trembler  transformer  types 224,  258 

operation  of  non-trembler 202 

screw-top  type 96 

transformer  types 200-226 

transformer,  use  of , 200 

trembler  of 204 

trembler  types,  complete 220-224 

trembler  type,  operation  of 205 

troubles 407 

varying  the  time  of  ignition  on  account  of  lag  in 361 

synchronized , 222 

Spark  control,  advance  must  be  excessive 420 

automatic 180 

Spark-gap,  safety 213 

width  of 238,  369 

Spark-plugs:  Jump-spark  igniters  are  indexed  under  Spark-plugs;  make-and- 
break  igniters  are  indexed  under  Igniters. 

Spark-plugs,  jump-spark 231-239 

Spark-plug,  adjusting  the  spark-gap 369 

Bosch  electromagnetic  low-tension,  small 192 

cleaning 369 

electromagnetic  low-tension,  small 191 

multiple  spark-gap  types 234 

screwing  into  place,  precaution 369 

separable  or  detachable 236 

spark-gap  width 238 

troubles 405 

Spark-plugs  in  series 261 

in  series-shunt 262 

Spark-points,  repairing,  in  contact  igniters 370 

Speed  governor 48 

Storage  batteries,  see  also  Batteries. 


436  INDEX 

PAGE 

Storage  batteries 97-1 10 

connection  for  charging  two  at  once 390 

Storage  battery,  action  of 97 

action  of  lead-plate  type 108 

ampere-hours  capacity 109 

capacity  and  size,  table 109 

care  of  lead-plate  type  of 390 

care  of  nickel-iron  type  of 394 

complete  lead-plate 99 

cell,  voltage  of  lead • 101 

charging 97,107 

charging  lead-plate  type  of 390 

charging  nickel-iron  type  of 394 

charging  and  care  of 387-396 

charging  rate 390,  393,  394 

connections  for  charging 388 

cover  vented 101 

defined 3 

density  of  electrolyte 386 

discharge  rate 102 

discharge  at  rapid  rate  injurious 102 

electrodes 97,  98,  99,  102 

electrolyte,  density  of 386 

electrolyte  for  lead-plate 101 

electrolyte,  mixing  for 392 

Exide 104 

floated  on  the  line no,  151 

floated,  APLCO  system 116 

as  formed  while  charging 108 

generator  and  lamp  combined  in  system no 

generator,  lamps  and  ignition  apparatus 114 

grids  of . 98,  107 

ignition  types 102,  107 

lead-plate  type 98 

lead  plates,  color  of 98 

plates  for 98,  99,  102 

rheostat  resistance  used  while  charging 389 

sediment  in 106 

sediment,  removing 393 

separator  for  plates  of 100,  106 

taking  out  of  commission 394,  396 

terminals  of 104 

testing 378-380 

testing  density  of  electrolyte 384 

test  by  voltage  and  current  method 278 

voltage  of 104,  395 

voltage,  lowest  safe 382 

voltage  while  discharging 383 


INDEX  437 

PAGE 

Storage  battery,  voltage-drop  test 381 

Switch,  kick-switch 222 

location  of,  in  make-and-break  system 151 

Switches,  reversing  the , . . 156,  158 

Switchboard,  automatic  cut-out  included 121 

combination  multiple 156,  162,  165,  166 

combination  no-volt 152-165 

combination  two-voltage 119,  121 

combination,  for  no  volts 152 

one-unit 152 

operation  of 156,  158 

reversing  the  switches 158,  161 

two  units 156,  162,  165 

two-voltage,  batteries  floated 119 

Tell-tale  kick-coil 142 

Tension,  electric,  defined I 

Terminals  of  battery 79,  89,  90 

Testing  a  battery 376 

density  of  electrolyte 384 

for  direction  of  current.  . 50 

lamp  for  battery 381 

a  storage  battery 378 

Timers 227-231 

Timer,  Allis-Chalmers 182 

automatic  control,  mechanism  for 180 

care  of 371 

elementary  form  of 227 

cleaning  and  lubricating 371 

four-ring  type  for  low-tension  ignition 182 

four-point  rotor 253 

for  large  engine 178 

one-ring  type  for  low-tension  ignition 178 

plain  pressure -contact  type 230 

roller  contact 227 

setting  in  position 398 

sliding-contact  type 229 

snap-spring  type 254 

speed  of 251 

troubles 408 

Wisconsin  Engine  Company's 178 

Timing  the  ignition 397-404 

automatic  mechanism  for 180 

Transformer  spark-coils,  see  also  Spark-coils. 

Transformer  spark-coils 200-226 

Trembler  of  spark-coil 204,  215,  217,  218,  219 

adjusting  the 370 

bow-spring  type 215 


438  INDEX 

PAGE 

Trembler,  hammer-break  types 217,  218 

plain  type 219 

Tritt  direct-current  magneto 49 

Troubles  and  remedies 405-420 

Unisparker 255,  259 

Voltage  of  a  battery 89 

of  carbon-zinc  diy-battery  cell 82 

of  carbon-zinc  wet-battery  cell 80 

of  copper  oxide  and  zinc  battery  cell 86 

of  parallel-connected  battery 90 

of  parallel-series  battery 92 

of  series-connected  battery 89 

of  storage  battery  while  discharging 383 

compound-wound  generator  for  constant 74 

Volt-ammeter 57 

in  an  electric  system 116 

Voltmeter,  dead-beat  needle  for 59 

direction  of  current  determined  with 53 

permanent,  in  jump-spark  ignition  system 249 

portable 56 

using 56 

Vibrator  of  spark-coil,  see  Trembler. 


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*  Waterbury's   Vest-Pocket   Hand-book  of   Mathematics  for   Engineers. 

2JX5I  inches,  mor.  1  00 

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16mo,  mor.  1  25 

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BRIDGES   AND  ROOFS. 

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*  Thames  River  Bridge Oblong  paper,  5  00 

Burr  and  Falk's  Design  and  Construction  of  Metallic  Bridges 8vo,  5  00 

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Du  Bois's  Mechanics  of  Engineering.     Vol.  II Sma  4to  ,  10  00 

Foster's  Treatise  on  Wooden  Trestle  Bridges 4to,  5  00 

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Modern  Framed  Structures Small  4to,  10  00 

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7 


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MATERIALS   OF   ENGINEERING. 

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Molitor  and  Beard's  Manual  for  Resident  Engineers 16mo,  1  00 

9 


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11       • 


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